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ASP.NET Core GraphQL Server

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# ASP.NET Core GraphQL Server driven by GraphQL.NET

[![License](https://img.shields.io/github/license/graphql-dotnet/server)](https://raw.githubusercontent.com/graphql-dotnet/server/master/LICENSE.md)
[![codecov](https://codecov.io/gh/graphql-dotnet/server/branch/master/graph/badge.svg?token=ZBcVYq7hz4)](https://codecov.io/gh/graphql-dotnet/server)
[![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.Transports.AspNetCore)](https://www.nuget.org/packages/GraphQL.Server.Transports.AspNetCore)
[![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.Transports.AspNetCore)](https://www.nuget.org/packages/GraphQL.Server.Transports.AspNetCore)
[![GitHub Release Date](https://img.shields.io/github/release-date/graphql-dotnet/server?label=released)](https://github.com/graphql-dotnet/server/releases)
[![GitHub commits since latest release (by date)](https://img.shields.io/github/commits-since/graphql-dotnet/server/latest?label=new+commits)](https://github.com/graphql-dotnet/server/commits/master)
[![GitHub contributors](https://img.shields.io/github/contributors/graphql-dotnet/server)](https://github.com/graphql-dotnet/server/graphs/contributors)
![Size](https://img.shields.io/github/repo-size/graphql-dotnet/server)

GraphQL ASP.NET Core server on top of [GraphQL.NET](https://github.com/graphql-dotnet/graphql-dotnet).
HTTP transport compatible with the [GraphQL over HTTP draft specification](https://github.com/graphql/graphql-over-http/blob/main/spec/GraphQLOverHTTP.md).
WebSocket transport compatible with both [subscriptions-transport-ws](https://github.com/apollographql/subscriptions-transport-ws) and
[graphql-ws](https://github.com/enisdenjo/graphql-ws) subscription protocols. The transport format of all messages is supposed to be JSON.

Provides the following packages:

| Package                                              | Downloads                                                                                                                                                                             | Version                                                                                                                                                                              | Description |
|------------------------------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|-------------|
| GraphQL.Server.All                                   | [![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.All)](https://www.nuget.org/packages/GraphQL.Server.All)                                                                     | [![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.All)](https://www.nuget.org/packages/GraphQL.Server.All)                                                                     | Includes all the packages below, plus the `GraphQL.DataLoader` and `GraphQL.MemoryCache` packages |
| GraphQL.Server.Transports.AspNetCore                 | [![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.Transports.AspNetCore)](https://www.nuget.org/packages/GraphQL.Server.Transports.AspNetCore)                                 | [![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.Transports.AspNetCore)](https://www.nuget.org/packages/GraphQL.Server.Transports.AspNetCore)                                 | Provides GraphQL over HTTP/WebSocket server support on top of ASP.NET Core, plus authorization rule support |
| GraphQL.Server.Ui.Altair                             | [![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.Ui.Altair)](https://www.nuget.org/packages/GraphQL.Server.Ui.Altair)                                                         | [![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.Ui.Altair)](https://www.nuget.org/packages/GraphQL.Server.Ui.Altair)                                                         | Provides Altair UI middleware |
| GraphQL.Server.Ui.Playground :warning:               | [![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.Ui.Playground)](https://www.nuget.org/packages/GraphQL.Server.Ui.Playground)                                                 | [![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.Ui.Playground)](https://www.nuget.org/packages/GraphQL.Server.Ui.Playground)                                                 | Provides Playground UI middleware (deprecated) |
| GraphQL.Server.Ui.GraphiQL                           | [![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.Ui.GraphiQL)](https://www.nuget.org/packages/GraphQL.Server.Ui.GraphiQL)                                                     | [![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.Ui.GraphiQL)](https://www.nuget.org/packages/GraphQL.Server.Ui.GraphiQL)                                                     | Provides GraphiQL UI middleware |
| GraphQL.Server.Ui.Voyager                            | [![Nuget](https://img.shields.io/nuget/dt/GraphQL.Server.Ui.Voyager)](https://www.nuget.org/packages/GraphQL.Server.Ui.Voyager)                                                       | [![Nuget](https://img.shields.io/nuget/v/GraphQL.Server.Ui.Voyager)](https://www.nuget.org/packages/GraphQL.Server.Ui.Voyager)                                                       | Provides Voyager UI middleware |

You can install the latest stable versions via [NuGet](https://www.nuget.org/packages/GraphQL.Server.Transports.AspNetCore/).
Also you can get all preview versions from [GitHub Packages](https://github.com/orgs/graphql-dotnet/packages?repo_name=server).
Note that GitHub requires authentication to consume the feed. See more information [here](https://docs.github.com/en/free-pro-team@latest/packages/publishing-and-managing-packages/about-github-packages#authenticating-to-github-packages).

| :warning: When upgrading from prior versions, please remove references to these old packages :warning: |
|-|
| GraphQL.Server.Core |
| GraphQL.Server.Authentication.AspNetCore |
| GraphQL.Server.Transports.AspNetCore.NewtonsoftJson |
| GraphQL.Server.Transports.AspNetCore.SystemTextJson |
| GraphQL.Server.Transports.Subscriptions.Abstractions |
| GraphQL.Server.Transports.Subscriptions.WebSockets |
| GraphQL.Server.Transports.WebSocktes |

## Description

This package is designed for ASP.NET Core (2.1 through 9.0) to facilitate easy set-up of GraphQL requests
over HTTP.  The code is designed to be used as middleware within the ASP.NET Core pipeline,
serving GET, POST or WebSocket requests.  GET requests process requests from the query string.
POST requests can be in the form of JSON requests, form submissions, or raw GraphQL strings.
Form submissions either accepts `query`, `operationName`, `variables` and `extensions` parameters,
or `operations` and `map` parameters along with file uploads as defined in the
[GraphQL multipart request spec](https://github.com/jaydenseric/graphql-multipart-request-spec).
WebSocket requests can use the `graphql-ws` or `graphql-transport-ws` WebSocket sub-protocol,
as defined in the [apollographql/subscriptions-transport-ws](https://github.com/apollographql/subscriptions-transport-ws)
and [enisdenjo/graphql-ws](https://github.com/enisdenjo/graphql-ws) repositories, respectively.

The middleware can be configured through the `IApplicationBuilder` or `IEndpointRouteBuilder`
builder interfaces.  Alternatively, route handlers (such as `MapGet` and `MapPost`) can return
a `GraphQLExecutionHttpResult` for direct GraphQL execution, or `ExecutionResultHttpResult` for
returning pre-executed GraphQL responses.  Similarly, `GraphQLExecutionActionResult`
and `ExecutionResultActionResult` classes can be used to return GraphQL responses from
controller actions.

Authorization is also supported with the included `AuthorizationValidationRule`.  It will
scan GraphQL documents and validate that the schema and all referenced output graph types, fields of
output graph types, and query arguments meet the specified policy and/or roles held by the
authenticated user within the ASP.NET Core authorization framework.  It does not validate
any policies or roles specified for input graph types, fields of input graph types, or
directives.  It skips validations for fields or fragments that are marked with the `@skip` or
`@include` directives.

### Migration from older version

- [v7 to v8 migration notes](docs/migration/migration8.md)
- [v6 to v7 migration notes](docs/migration/migration7.md)

## Configuration

### Typical configuration with HTTP middleware

First add either the `GraphQL.Server.All` nuget package or the `GraphQL.Server.Transports.AspNetCore`
nuget package to your application.  Referencing the "all" package will include the UI middleware
packages.  These packages depend on `GraphQL` version 8.2.1 or later.

Then update your `Program.cs` or `Startup.cs` to configure GraphQL, registering the schema
and the serialization engine as a minimum.  Configure WebSockets and GraphQL in the HTTP
pipeline by calling `UseWebSockets` and `UseGraphQL` at the appropriate point.
Finally, you may also include some UI middleware for easy testing of your GraphQL endpoint
by calling `UseGraphQLGraphiQL` or a similar method at the appropriate point.

Below is a complete sample of a .NET 6 console app that hosts a GraphQL endpoint at
`http://localhost:5000/graphql`:

#### Project file

```xml
<Project Sdk="Microsoft.NET.Sdk.Web">

<PropertyGroup>
    <TargetFramework>net6.0</TargetFramework>
    <ImplicitUsings>enable</ImplicitUsings>
    <Nullable>enable</Nullable>
  </PropertyGroup>

</Project>
```

#### Program.cs file

```csharp
using GraphQL;

var builder = WebApplication.CreateBuilder(args);
builder.Services.AddGraphQL(b => b
    .AddAutoSchema<Query>()  // schema
    .AddSystemTextJson());   // serializer

var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseWebSockets();
app.UseGraphQL("/graphql");            // url to host GraphQL endpoint
app.UseGraphQLGraphiQL(
    "/",                               // url to host GraphiQL at
    new GraphQL.Server.Ui.GraphiQL.GraphiQLOptions
    {
        GraphQLEndPoint = "/graphql",         // url of GraphQL endpoint
        SubscriptionsEndPoint = "/graphql",   // url of GraphQL endpoint
    });
await app.RunAsync();
```

#### Schema

```csharp
public class Query
{
    public static string Hero() => "Luke Skywalker";
}
```

#### Sample request url

```
http://localhost:5000/graphql?query={hero}
```

#### Sample response

```json
{"data":{"hero":"Luke Skywalker"}}
```

### Basic options

By default, the middleware will be installed with these configurable options:
- GET, POST, and WebSocket requests are all enabled
- Form content types are disabled, and cross-site request forgery (CSRF)
  protection is enabled
- There are no authentication or authorization requirements
- The default response content type is `application/graphql-response+json`
- The middleware will use the default schema instance

To configure these options, pass a confiuguration delegate to the `UseGraphQL`
method as demonstrated below:

```csharp
app.UseGraphQL("/graphql", opts => {
    opts.ReadFormOnPost = true;
});
```

Configuration of these options and more are further described below in this document.

### Configuration with endpoint routing

To use endpoint routing, call `MapGraphQL` from inside the endpoint configuration
builder rather than `UseGraphQL` on the application builder.  See below for the
sample of the application builder code:

```csharp
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseWebSockets();
app.UseRouting();
app.UseEndpoints(endpoints =>
{
    endpoints.MapGraphQL("graphql");
    endpoints.MapGraphQLVoyager("ui/voyager");
});
await app.RunAsync();
```

Using endpoint routing is particularly useful when you want to select a specific
CORS configuration for the GraphQL endpoint.  See the CORS section below for a sample.

Please note that when using endpoint routing, you cannot use WebSocket connections
while a UI package is also configured at the same URL.  You will need to use a
different URL for the UI package, or use UI middleware prior to endpoint routing.
So long as different URLs are used, there are no issues.  Below is a sample when
the UI and GraphQL reside at the same URL:

```csharp
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseWebSockets();
app.UseRouting();
app.UseGraphQLVoyager("/graphql");
app.UseEndpoints(endpoints =>
{
    endpoints.MapGraphQL("/graphql");
});
await app.RunAsync();
```

### Configuration with route handlers (.NET 6+)

Although not recommended, you may set up [route handlers](https://learn.microsoft.com/en-us/aspnet/core/fundamentals/minimal-apis/route-handlers)
to execute GraphQL requests using `MapGet` and `MapPost` that return an `IResult`.
You will not need `UseGraphQL` or `MapGraphQL` in the application startup.  Note that GET must be
mapped to support WebSocket connections, as WebSocket connections upgrade from HTTP GET requests.

#### Using `GraphQLExecutionHttpResult`

```csharp
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseWebSockets();

// configure the graphql endpoint at "/graphql", using GraphQLExecutionHttpResult
// map GET in order to support both GET and WebSocket requests
app.MapGet("/graphql", () => new GraphQLExecutionHttpResult());
// map POST to handle standard GraphQL POST requests
app.MapPost("/graphql", () => new GraphQLExecutionHttpResult());

await app.RunAsync();
```

#### Using `ExecutionResultHttpResult`

```csharp
app.MapPost("/graphql", async (HttpContext context, IDocumentExecuter<ISchema> documentExecuter, IGraphQLSerializer serializer) =>
{
    var request = await serializer.ReadAsync<GraphQLRequest>(context.Request.Body, context.RequestAborted);
    var opts = new ExecutionOptions
    {
        Query = request?.Query,
        DocumentId = request?.DocumentId,
        Variables = request?.Variables,
        Extensions = request?.Extensions,
        CancellationToken = context.RequestAborted,
        RequestServices = context.RequestServices,
        User = context.User,
    };

return new ExecutionResultHttpResult(await documentExecuter.ExecuteAsync(opts));
});
```

### Configuration with a MVC controller

Although not recommended, you may set up a controller action to execute GraphQL
requests.  You will not need `UseGraphQL` or `MapGraphQL` in the application
startup.  You may use `GraphQLExecutionActionResult` to let the middleware
handle the entire parsing and execution of the request, including subscription
requests over WebSocket connections, or you can execute the request yourself,
only using `ExecutionResultActionResult` to serialize the result.

You can also reference the UI projects to display a GraphQL user interface as shown below.

#### Using `GraphQLExecutionActionResult`

```csharp
public class HomeController : Controller
{
    public IActionResult Index()
        => new GraphiQLActionResult(opts =>
        {
            opts.GraphQLEndPoint = "/Home/graphql";
            opts.SubscriptionsEndPoint = "/Home/graphql";
        });

[HttpGet]
    [HttpPost]
    [ActionName("graphql")]
    public IActionResult GraphQL()
        => new GraphQLExecutionActionResult();
}
```

#### Using `ExecutionResultActionResult`

Note: this is very simplified; a much more complete sample can be found
in the `Samples.Controller` project within this repository.

```csharp
public class HomeController : Controller
{
    private readonly IDocumentExecuter _documentExecuter;

public TestController(IDocumentExecuter<ISchema> documentExecuter)
    {
        _documentExecuter = documentExecuter;
    }

[HttpGet]
    public async Task<IActionResult> GraphQL(string query)
    {
        var result = await _documentExecuter.ExecuteAsync(new()
        {
            Query = query,
            RequestServices = HttpContext.RequestServices,
            CancellationToken = HttpContext.RequestAborted,
        });
        return new ExecutionResultActionResult(result);
    }
}
```

### Configuration with Azure Functions

This project also supports hosting GraphQL endpoints within Azure Functions.
You will need to complete the following steps:

1. Configure the Azure Function to use Dependency Injection:
   See https://learn.microsoft.com/en-us/azure/azure-functions/functions-dotnet-dependency-injection
   for details.

2. Configure GraphQL via `builder.Services.AddGraphQL()` the same as you would in a typical
   ASP.NET Core application.

3. Add an HTTP function that returns an appropriate `ActionResult`:

```csharp
[FunctionName("GraphQL")]
public static IActionResult RunGraphQL(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get", "post"] HttpRequest req)
{
    return new GraphQLExecutionActionResult();
}
```

4. Optionally, add a UI package to the project and configure it:

```csharp
[FunctionName("GraphiQL")]
public static IActionResult RunGraphiQL(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get"] HttpRequest req)
{
    return new GraphiQLActionResult(opts => opts.GraphQLEndPoint = "/api/graphql");
}
```

Middleware can be configured by passing a configuration delegate to `new GraphQLExecutionActionResult()`.
Multiple schemas are supported by the use of `GraphQLExecutionActionResult<TSchema>()`.
It is not possible to configure subscription support, as Azure Functions do not support WebSockets
since it is a serverless environment.

See the `Samples.AzureFunctions` project for a complete sample based on the
.NET template for Azure Functions.

Please note that the GraphQL schema needs to be initialized for every call through
Azure Functions, since it is a serverless environment.  This is done automatically
but will come at a performance cost.  If you are using a schema that is expensive
to initialize, you may want to consider using a different hosting environment.

### User context configuration

To set the user context to be used during the execution of GraphQL requests,
call `AddUserContextBuilder` during the GraphQL service setup to set a delegate
which will be called when the user context is built.  Alternatively, you can
register an `IUserContextBuilder` implementation to do the same.

#### Program.cs / Startup.cs

```csharp
builder.Services.AddGraphQL(b => b
    .AddAutoSchema<Query>()
    .AddSystemTextJson()
    .AddUserContextBuilder(httpContext => new MyUserContext(httpContext));
```

#### MyUserContext.cs

```csharp
public class MyUserContext : Dictionary<string, object?>
{
    public ClaimsPrincipal User { get; }

public MyUserContext(HttpContext context)
    {
        User = context.User;
    }
}
```

### Authorization configuration

You can configure authorization for all GraphQL requests, or for individual
graphs, fields and query arguments within your schema.  Both can be used
if desired.

Be sure to call `app.UseAuthentication()` and `app.UseAuthorization()` prior
to the call to `app.UseGraphQL()`.  For example:

```csharp
app.UseAuthentication();
app.UseAuthorization();
app.UseWebSockets();
app.UseGraphQL("/graphql");
```

#### Endpoint authorization (which would include introspection requests)

Endpoint authorization will check authorization requirements are met for the entire
GraphQL endpoint, including introspection requests.  These checks occur prior to parsing,
validating or executing the document.

When calling `UseGraphQL`, specify options as necessary to configure authorization as required.

```csharp
app.UseGraphQL("/graphql", config =>
{
    // require that the user be authenticated
    config.AuthorizationRequired = true;

// require that the user be a member of at least one role listed
    config.AuthorizedRoles.Add("MyRole");
    config.AuthorizedRoles.Add("MyAlternateRole");

// require that the user pass a specific authorization policy
    config.AuthorizedPolicy = "MyPolicy";
});
```

#### For individual graph types, fields and query arguments

To configure the ASP.NET Core authorization validation rule for GraphQL, add the corresponding
validation rule during GraphQL configuration, typically by calling `.AddAuthorizationRule()`
as shown below:

```csharp
builder.Services.AddGraphQL(b => b
    .AddAutoSchema<Query>()
    .AddSystemTextJson()
    .AddAuthorizationRule());
```

Both roles and policies are supported for output graph types, fields on output graph types,
and query arguments.  If multiple policies are specified, all must match; if multiple roles
are specified, any one role must match.  You may also use `.Authorize()` and/or the
`[Authorize]` attribute to validate that the user has authenticated.  You may also use
`.AllowAnonymous()` and/or `[AllowAnonymous]` to allow fields to bypass authorization
requirements defined on the type that contains the field.

Please note that authorization rules do not apply to values returned within introspection requests,
potentially leaking information about protected areas of the schema to unauthenticated users.
You may use the `ISchemaFilter` to restrict what information is returned from introspection
requests, but it will apply to both authenticated and unauthenticated users alike.

Introspection requests are allowed unless the schema has an authorization requirement set on it.
The `@skip` and `@include` directives are honored, skipping authorization checks for fields
or fragments skipped by `@skip` or `@include`.

Please note that if you use interfaces, validation might be executed against the graph field
or the interface field, depending on the structure of the query.  For instance:

```graphql
{
  cat {
    # validates against Cat.Name
    name

# validates against Animal.Name
    ... on Animal {
      name
    }
  }
}
```

Similarly for unions, validation occurs on the exact type that is queried.  Be sure to carefully
consider placement of authorization rules when using interfaces and unions, especially when some
fields are marked with `AllowAnonymous`.

| :warning: Note that authorization rules are ignored for input types and fields of input types :warning: |
|-|

#### Custom authentication configuration for GET/POST requests

To provide custom authentication code, bypassing ASP.NET Core's authentication, derive from the
`GraphQLHttpMiddleware<T>` class and override `HandleAuthorizeAsync`, setting `HttpContext.User`
to an appropriate `ClaimsPrincipal` instance.

See 'Customizing middleware behavior' below for an example of deriving from `GraphQLHttpMiddleware`.

#### Authentication for WebSocket requests

Since WebSocket requests from browsers cannot typically carry a HTTP Authorization header, you
will need to authorize requests via the `ConnectionInit` WebSocket message or carry the authorization
token within the URL.  Below is a sample of the former:

```cs
builder.Services.AddGraphQL(b => b
    .AddAutoSchema<Query>()
    .AddSystemTextJson()
    .AddAuthorizationRule()  // not required for endpoint authorization
    .AddWebSocketAuthentication<MyAuthService>());

app.UseGraphQL("/graphql", config =>
{
    // require that the user be authenticated
    config.AuthorizationRequired = true;
});

class MyAuthService : IWebSocketAuthenticationService
{
    private readonly IGraphQLSerializer _serializer;

public MyAuthService(IGraphQLSerializer serializer)
    {
        _serializer = serializer;
    }

public async ValueTask<bool> AuthenticateAsync(IWebSocketConnection connection, OperationMessage operationMessage)
    {
        // read payload of ConnectionInit message and look for an "Authorization" entry that starts with "Bearer "
        var payload = _serializer.ReadNode<Inputs>(operationMessage.Payload);
        if ((payload?.TryGetValue("Authorization", out var value) ?? false) && value is string valueString)
        {
            var user = ParseToken(valueString);
            if (user != null)
            {
                // set user and indicate authentication was successful
                connection.HttpContext.User = user;
                return true;
            }
        }
        return false; // authentication failed
    }

private ClaimsPrincipal? ParseToken(string authorizationHeaderValue)
    {
        // parse header value and return user, or null if unable
    }
}
```

To authorize based on information within the query string, it is recommended to
derive from `GraphQLHttpMiddleware<T>` and override `InvokeAsync`, setting
`HttpContext.User` based on the query string parameters, and then calling `base.InvokeAsync`.
Alternatively you may override `HandleAuthorizeAsync` which will execute for GET/POST requests,
and `HandleAuthorizeWebSocketConnectionAsync` for WebSocket requests.
Note that `InvokeAsync` will execute even if the protocol is disabled in the options via
disabling `HandleGet` or similar; `HandleAuthorizeAsync` and `HandleAuthorizeWebSocketConnectionAsync`
will not.

#### Authentication schemes

By default the role and policy requirements are validated against the current user as defined by
`HttpContext.User`.  This is typically set by ASP.NET Core's authentication middleware and is based
on the default authentication scheme set during the call to `AddAuthentication` in `Startup.cs`.
You may override this behavior by specifying a different authentication scheme via the `AuthenticationSchemes`
option.  For instance, if you wish to authenticate using JWT authentication when Cookie authentication is
the default, you may specify the scheme as follows:

```csharp
app.UseGraphQL("/graphql", config =>
{
    // specify a specific authentication scheme to use
    config.AuthenticationSchemes.Add(JwtBearerDefaults.AuthenticationScheme);
});
```

This will overwrite the `HttpContext.User` property when handling GraphQL requests, which will in turn
set the `IResolveFieldContext.User` property to the same value (unless being overridden via an
`IWebSocketAuthenticationService` implementation as shown above).  So both endpoint authorization and
field authorization will perform role and policy checks against the same authentication scheme.

### UI configuration

There are four UI middleware projects included; Altair, GraphiQL, Playground and Voyager.
Playground has not been updated since 2019 and is deprecated in favor of GraphiQL.
See review the following methods for configuration options within each of the 4 respective
NuGet packages:

```csharp
app.UseGraphQLAltair();
app.UseGraphQLGraphiQL();
app.UseGraphQLPlayground();  // deprecated
app.UseGraphQLVoyager();

// or

endpoints.MapGraphQLAltair();
endpoints.MapGraphQLGraphiQL();
endpoints.MapGraphQLPlayground();  // deprecated
endpoints.MapGraphQLVoyager();
```

### CORS configuration

ASP.NET Core supports CORS requests independently of GraphQL, including CORS pre-flight
requests.  To configure your application for CORS requests, add `AddCors()` and `UseCors()`
into the application pipeline.

```csharp
builder.Services.AddCors();

app.UseCors(policy => {
    // configure default policy here
});
```

To configure GraphQL to use a named CORS policy, configure the application to use endpoint routing
and call `RequireCors()` on the endpoint configuration builder.

```csharp
// ...
builder.Services.AddRouting();
builder.Services.AddCors(builder =>
{
    // configure named and/or default policies here
});

var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseWebSockets();
app.UseRouting();
app.UseCors();
app.UseEndpoints(endpoints =>
{
    // configure the graphql endpoint with the specified CORS policy
    endpoints.MapGraphQL()
        .RequireCors("MyCorsPolicy");
});
await app.RunAsync();
```

In order to ensure that all requests trigger CORS preflight requests, by default the server
will reject requests that do not meet one of the following criteria:

- The request is a POST request that includes a Content-Type header that is not
  `application/x-www-form-urlencoded`, `multipart/form-data`, or `text/plain`.
- The request includes a non-empty `GraphQL-Require-Preflight` header.

To disable this behavior, set the `CsrfProtectionEnabled` option to `false`.

```csharp
app.UseGraphQL("/graphql", config =>
{
    config.CsrfProtectionEnabled = false;
});
```

You may also change the allowed headers by modifying the `CsrfProtectionHeaders` option.

```csharp
app.UseGraphQL("/graphql", config =>
{
    config.CsrfProtectionHeaders = ["MyCustomHeader"];
});
```

### Response compression

ASP.NET Core supports response compression independently of GraphQL, with brotli and gzip
support automatically based on the compression formats listed as supported in the request headers.
To configure your application for response compression, configure your Program/Startup file as
follows:

```csharp
// add and configure the service
builder.Services.AddResponseCompression(options =>
{
    options.EnableForHttps = true; // may lead to CRIME and BREACH attacks
    options.MimeTypes = ResponseCompressionDefaults.MimeTypes.Append("application/graphql-response+json");
})

// place this first/early in the pipeline
app.UseResponseCompression();
```

In order to compress GraphQL responses, the `application/graphql-response+json` content type must be
added to the `MimeTypes` option.  You may choose to enable other content types as well.

Please note that enabling response compression over HTTPS can lead to CRIME and BREACH
attacks.  These side-channel attacks typically affects sites that rely on cookies for
authentication.  Please read [this](https://docs.microsoft.com/en-us/aspnet/core/performance/response-compression)
and [this](http://www.breachattack.com/#howitworks) for more details.

### ASP.NET Core 2.1 / .NET Framework 4.8

You may choose to use the .NET Core 2.1 runtime or the .NET Framework 4.8 runtime.
This library has been tested with .NET Core 2.1 and .NET Framework 4.8.

The only additional requirement is that you must add this code in your `Startup.cs` file:

```csharp
services.AddHostApplicationLifetime();
```

Besides that requirement, all features are supported in exactly the same manner as
when using ASP.NET Core 3.1+.  You may find differences in the ASP.NET Core runtime,
such as CORS implementation differences, which are outside the scope of this project.

Please note that a serializer reference is not included for these projects within
`GraphQL.Server.Transports.AspNetCore`; you will need to reference either
`GraphQL.NewtonsoftJson` or `GraphQL.SystemTextJson`, or reference
`GraphQL.Server.All` which includes `GraphQL.NewtonsoftJson` for ASP.NET Core 2.1 projects.
This is because `Newtonsoft.Json` is the default serializer for ASP.NET Core 2.1
rather `System.Text.Json`.  When using `GraphQL.NewtonsoftJson`, you will need to call
`AddNewtonsoftJson()` rather than `AddSystemTextJson()` while configuring GraphQL.NET.

<details><summary>Microsoft support policy</summary><p>

Please note that .NET Core 2.1 is currently out of support by Microsoft.
.NET Framework 4.8 is supported, and ASP.NET Core 2.1 is supported when run on
.NET Framework 4.8.  Please see these links for more information:

- https://dotnet.microsoft.com/en-us/platform/support/policy/dotnet-framework
- https://dotnet.microsoft.com/en-us/platform/support/policy/aspnetcore-2.1

</p></details>

## Advanced configuration

For more advanced configurations, see the overloads and configuration options
available for the various builder methods, listed below.  Methods and properties
contain XML comments to provide assistance while coding with your IDE.

| Builder interface       | Method                  | Description |
|-------------------------|-------------------------|-------------|
| `IGraphQLBuilder`       | `AddUserContextBuilder` | Sets up a delegate to create the UserContext for each GraphQL request. |
| `IApplicationBuilder`   | `UseGraphQL`            | Adds the GraphQL middleware to the HTTP request pipeline. |
| `IEndpointRouteBuilder` | `MapGraphQL`            | Adds the GraphQL middleware to the HTTP request pipeline. |

A number of the methods contain optional parameters or configuration delegates to
allow further customization.  Please review the overloads of each method to determine
which options are available.  In addition, many methods have more descriptive XML
comments than shown above.

### Configuration options

Below are descriptions of the options available when registering the HTTP middleware.
Note that the HTTP middleware options are configured via the `UseGraphQL` or `MapGraphQL`
methods allowing for different options for each configured endpoint.

#### GraphQLHttpMiddlewareOptions

| Property                           | Description     | Default value |
|------------------------------------|-----------------|---------------|
| `AuthorizationRequired`            | Requires `HttpContext.User` to represent an authenticated user. | False |
| `AuthorizedPolicy`                 | If set, requires `HttpContext.User` to pass authorization of the specified policy. | |
| `AuthorizedRoles`                  | If set, requires `HttpContext.User` to be a member of any one of a list of roles. | |
| `CsrfProtectionEnabled`            | Enables cross-site request forgery (CSRF) protection for both GET and POST requests. | True |
| `CsrfProtectionHeaders`            | Sets the headers used for CSRF protection when necessary. | `GraphQL-Require-Preflight` |
| `DefaultResponseContentType`       | Sets the default response content type used within responses. | `application/graphql-response+json; charset=utf-8` |
| `EnableBatchedRequests`            | Enables handling of batched GraphQL requests for POST requests when formatted as JSON. | True |
| `ExecuteBatchedRequestsInParallel` | Enables parallel execution of batched GraphQL requests. | True |
| `HandleGet`                        | Enables handling of GET requests. | True |
| `HandlePost`                       | Enables handling of POST requests. | True |
| `HandleWebSockets`                 | Enables handling of WebSockets requests. | True |
| `MaximumFileSize`                  | Sets the maximum file size allowed for GraphQL multipart requests. | unlimited |
| `MaximumFileCount`                 | Sets the maximum number of files allowed for GraphQL multipart requests. | unlimited |
| `ReadExtensionsFromQueryString`    | Enables reading extensions from the query string. | True |
| `ReadFormOnPost`                   | Enables parsing of form data for POST requests (may have security implications). | False |
| `ReadQueryStringOnPost`            | Enables parsing the query string on POST requests. | True |
| `ReadVariablesFromQueryString`     | Enables reading variables from the query string. | True |
| `ValidationErrorsReturnBadRequest` | When enabled, GraphQL requests with validation errors have the HTTP status code set to 400 Bad Request. | Automatic[^1] |
| `WebSockets`                       | Returns a set of configuration properties for WebSocket connections. | |

[^1]: Automatic mode will return a 200 OK status code when the returned content type is `application/json`; otherwise 400 or as defined by the error.

#### GraphQLWebSocketOptions

| Property                    | Description          | Default value |
|-----------------------------|----------------------|---------------|
| `ConnectionInitWaitTimeout` | The amount of time to wait for a GraphQL initialization packet before the connection is closed. | 10 seconds |
| `DisconnectionTimeout`      | The amount of time to wait to attempt a graceful teardown of the WebSockets protocol. | 10 seconds |
| `DisconnectAfterErrorEvent` | Disconnects a subscription from the client if the subscription source dispatches an `OnError` event. | True |
| `DisconnectAfterAnyError`   | Disconnects a subscription from the client if there are any GraphQL errors during a subscription. | False |
| `KeepAliveMode`             | The mode to use for sending keep-alive packets. | protocol-dependent |
| `KeepAliveTimeout`          | The amount of time to wait between sending keep-alive packets. | disabled |
| `SupportedWebSocketSubProtocols` | A list of supported WebSocket sub-protocols. | `graphql-ws`, `graphql-transport-ws` |

### Multi-schema configuration

You may use the generic versions of the various builder methods to map a URL to a particular schema.

```csharp
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseGraphQL<DogSchema>("/dogs/graphql");
app.UseGraphQL<CatSchema>("/cats/graphql");
await app.RunAsync();
```

### Different global authorization settings for different transports (GET/POST/WebSockets)

You may register the same endpoint multiple times if necessary to configure GET connections
with certain authorization options, and POST connections with other authorization options.

```csharp
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseGraphQL("/graphql", options =>
{
    options.HandleGet = true;
    options.HandlePost = false;
    options.HandleWebSockets = false;
    options.AuthorizationRequired = false;
});
app.UseGraphQL("/graphql", options =>
{
    options.HandleGet = false;
    options.HandlePost = true;
    options.HandleWebSockets = true;
    options.AuthorizationRequired = true;   // require authentication for POST/WebSocket connections
});
await app.RunAsync();
```

Since POST and WebSockets can be used for query requests, it is recommended not to do the above,
but instead add the authorization validation rule and add authorization metadata on the Mutation
and Subscription portions of your schema, as shown below:

```csharp
builder.Services.AddGraphQL(b => b
    .AddSchema<MySchema>()
    .AddSystemTextJson()
    .AddAuthorizationRule()); // add authorization validation rule

var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseGraphQL();
await app.RunAsync();

// demonstration of code-first schema; also possible with schema-first or type-first schemas
public class MySchema : Schema
{
    public MySchema(IServiceProvider provider, MyQuery query, MyMutation mutation) : base(provider)
    {
        Query = query;
        Mutation = mutation;

mutation.Authorize(); // require authorization for any mutation request
    }
}
```

### Keep-alive configuration

By default, the middleware will not send keep-alive packets to the client.  As the underlying
operating system may not detect a disconnected client until a message is sent, you may wish to
enable keep-alive packets to be sent periodically.  The default mode for keep-alive packets
differs depending on whether the client connected with the `graphql-ws` or `graphql-transport-ws`
sub-protocol.  The `graphql-ws` sub-protocol will send a unidirectional keep-alive packet to the
client on a fixed schedule, while the `graphql-transport-ws` sub-protocol will only send
unidirectional keep-alive packets when the client has not sent a message within a certain time.
The differing behavior is due to the default implementation of the `graphql-ws` sub-protocol
client, which after receiving a single keep-alive packet, expects additional keep-alive packets
to be sent sooner than every 20 seconds, regardless of the client's activity.

To configure keep-alive packets, set the `KeepAliveMode` and `KeepAliveTimeout` properties
within the `GraphQLWebSocketOptions` object.  Set the `KeepAliveTimeout` property to
enable keep-alive packets, or use `TimeSpan.Zero` or `Timeout.InfiniteTimeSpan` to disable it.

The `KeepAliveMode` property is only applicable to the `graphql-transport-ws` sub-protocol and
can be set to the options listed below:

| Keep-alive mode | Description |
|-----------------|-------------|
| `Default`       | Same as `Timeout`. |
| `Timeout`       | Sends a unidirectional keep-alive message when no message has been received within the specified timeout period. |
| `Interval`      | Sends a unidirectional keep-alive message at a fixed interval, regardless of message activity. |
| `TimeoutWithPayload` | Sends a bidirectional keep-alive message with a payload on a fixed interval, and validates the payload matches in the response. |

The `TimeoutWithPayload` model is particularly useful when the server may send messages to the
client at a faster pace than the client can process them.  In this case queued messages will be
limited to double the timeout period, as the keep-alive message is queued along with other
packets sent from the server to the client.  The client will need to respond to process queued
messages and respond to the keep-alive message within the timeout period or the server will
disconnect the client.  When the server forcibly disconnects the client, no graceful teardown
of the WebSocket protocol occurs, and any queued messages are discarded.

When using the `TimeoutWithPayload` keep-alive mode, you may wish to enforce that the
`graphql-transport-ws` sub-protocol is in use by the client, as the `graphql-ws` sub-protocol
does not support bidirectional keep-alive packets.  This can be done by setting the
`SupportedWebSocketSubProtocols` property to only include the `graphql-transport-ws` sub-protocol.

```csharp
app.UseGraphQL("/graphql", options =>
{
    // configure keep-alive packets
    options.WebSockets.KeepAliveTimeout = TimeSpan.FromSeconds(10);
    options.WebSockets.KeepAliveMode = KeepAliveMode.TimeoutWithPayload;
    // set the supported sub-protocols to only include the graphql-transport-ws sub-protocol
    options.WebSockets.SupportedWebSocketSubProtocols = [GraphQLWs.SubscriptionServer.SubProtocol];
});
```

Please note that the included UI packages are configured to use the `graphql-ws` sub-protocol by
default.  You may use the `graphql-transport-ws` sub-protocol with the GraphiQL package by setting
the `GraphQLWsSubscriptions` option to `true` when configuring the GraphiQL middleware.

### Customizing middleware behavior

GET/POST requests are handled directly by the `GraphQLHttpMiddleware`.
For WebSocket requests an `WebSocketConnection` instance is created to dispatch incoming
messages and send outgoing messages.  Depending on the WebSocket sub-protocols supported by the
client, the proper implementation of `IOperationMessageProcessor` is created to act as a
state machine, processing incoming messages and sending outgoing messages through the
`WebSocketConnection` instance.

#### GraphQLHttpMiddleware

The base middleware functionality is contained within `GraphQLHttpMiddleware`, with code
to perform execution of GraphQL requests in the derived class `GraphQLHttpMiddleware<TSchema>`.
The classes are organized as follows:

- `InvokeAsync` is the entry point to the middleware.  For WebSocket connection requests,
  execution is immediately passed to `HandleWebSocketAsync`.
- Methods that start with `Handle` are passed the `HttpContext` and `RequestDelegate`
  instance, and may handle the request or pass execution to the `RequestDelegate` thereby
  skipping this execution handler.  This includes methods to handle execution of single or
  batch queries or returning error conditions.
- Methods that start with `Write` are for writing responses to the output stream.
- Methods that start with `Execute` are for executing GraphQL requests.

A list of methods are as follows:

| Method                      | Description |
|-----------------------------|-------------|
| `InvokeAsync`               | Entry point of the middleware |
| `HandleRequestAsync`        | Handles a single GraphQL request. |
| `HandleBatchRequestAsync`   | Handles a batched GraphQL request. |
| `HandleWebSocketAsync`      | Handles a WebSocket connection request. |
| `BuildUserContextAsync`     | Builds the user context based on a `HttpContext`. |
| `ExecuteRequestAsync`       | Executes a GraphQL request. |
| `ExecuteScopedRequestAsync` | Executes a GraphQL request with a scoped service provider. |
| `SelectResponseContentType` | Selects a content-type header for the JSON-formatted GraphQL response. |
| `WriteErrorResponseAsync`   | Writes the specified error message as a JSON-formatted GraphQL response, with the specified HTTP status code. |
| `WriteJsonResponseAsync`    | Writes the specified object (usually a GraphQL response) as JSON to the HTTP response stream. |

| Error handling method                         | Description |
|-----------------------------------------------|-------------|
| `HandleBatchedRequestsNotSupportedAsync`      | Writes a '400 Batched requests are not supported.' message to the output. |
| `HandleContentTypeCouldNotBeParsedErrorAsync` | Writes a '415 Invalid Content-Type header: could not be parsed.' message to the output. |
| `HandleDeserializationErrorAsync`             | Writes a '400 JSON body text could not be parsed.' message to the output. |
| `HandleInvalidContentTypeErrorAsync`          | Writes a '415 Invalid Content-Type header: non-supported type.' message to the output. |
| `HandleInvalidHttpMethodErrorAsync`           | Indicates that an unsupported HTTP method was requested. Executes the next delegate in the chain by default. |
| `HandleWebSocketSubProtocolNotSupportedAsync` | Writes a '400 Invalid WebSocket sub-protocol.' message to the output. |

Below is a sample of custom middleware to change the response content type to `application/json`,
regardless of the value of the HTTP 'Accept' header or default value set in the options:

```csharp
class MyMiddleware<TSchema> : GraphQLHttpMiddleware<TSchema>
    where TSchema : ISchema
{
    public MyMiddleware(
        RequestDelegate next,
        IGraphQLTextSerializer serializer,
        IDocumentExecuter<TSchema> documentExecuter,
        IServiceScopeFactory serviceScopeFactory,
        GraphQLHttpMiddlewareOptions options,
        IHostApplicationLifetime hostApplicationLifetime)
        : base(next, serializer, documentExecuter, serviceScopeFactory, options, hostApplicationLifetime)
    {
    }

protected override string SelectResponseContentType(HttpContext context)
        => "application/json";
}

app.UseGraphQL<MyMiddleware<ISchema>>("/graphql", new GraphQLHttpMiddlewareOptions());
```

Be sure to derive from `GraphQLHttpMiddleware<TSchema>` rather than `GraphQLHttpMiddleware`
as shown above for multi-schema compatibility.

#### WebSocket handler classes

The WebSocket handling code is organized as follows:

| Interface / Class                | Description |
|----------------------------------|-------------|
| `IWebSocketConnection`           | Provides methods to send a message to a client or close the connection. |
| `IOperationMessageProcessor`     | Handles incoming messages from the client. |
| `GraphQLWebSocketOptions`        | Provides configuration options for WebSocket connections. |
| `WebSocketConnection`            | Standard implementation of a message pump for `OperationMessage` messages across a WebSockets connection.  Implements `IWebSocketConnection` and delivers messages to a specified `IOperationMessageProcessor`. |
| `BaseSubscriptionServer`         | Abstract implementation of `IOperationMessageProcessor`, a message handler for `OperationMessage` messages.  Provides base functionality for managing subscriptions and requests. |
| `GraphQLWs.SubscriptionServer`   | Implementation of `IOperationMessageProcessor` for the `graphql-transport-ws` sub-protocol. |
| `SubscriptionsTransportWs.SubscriptionServer` | Implementation of `IOperationMessageProcessor` for the `graphql-ws` sub-protocol. |
| `IWebSocketAuthorizationService` | Allows authorization of GraphQL requests for WebSocket connections. |

Typically if you wish to change functionality or support another sub-protocol
you will need to perform the following:

1. Derive from either `SubscriptionServer` class, modifying functionality as needed, or to support
   a new protocol, derive from `BaseSubscriptionServer`.
2. Derive from `GraphQLHttpMiddleware<T>` and override `CreateMessageProcessor` and/or
   `SupportedWebSocketSubProtocols` as needed.
3. Change the `app.AddGraphQL()` call to use your custom middleware, being sure to include an instance
   of the options class that your middleware requires (typically `GraphQLHttpMiddlewareOptions`).

There exists a few additional classes to support the above.  Please refer to the source code
of `GraphQLWs.SubscriptionServer` if you are attempting to add support for another protocol.

## Additional notes / FAQ

### Service scope

By default, a dependency injection service scope is created for each GraphQL execution
in cases where it is possible that multiple GraphQL requests may be executing within the
same service scope:

1. A batched GraphQL request is executed.
2. A GraphQL request over a WebSocket connection is executed.

However, field resolvers for child fields of subscription nodes will not by default execute
with a service scope.  Rather, the `context.RequestServices` property will contain a reference
to a disposed service scope that cannot be used.

To solve this issue, please configure the scoped subscription execution strategy from the
GraphQL.MicrosoftDI package as follows:

```csharp
services.AddGraphQL(b => b
    .AddAutoSchema<Query>()
    .AddSystemTextJson()
    // configure queries for serial execution (optional)
    .AddExecutionStrategy<SerialExecutionStrategy>(OperationType.Query)
    // configure subscription field resolvers for scoped serial execution (parallel is optional)
    .AddScopedSubscriptionExecutionStrategy());
```

For single GET / POST requests, the service scope from the underlying HTTP context is used.

### User context builder

The user context builder interface is executed only once, within the dependency injection
service scope of the original HTTP request.  For batched requests, the same user context
instance is passed to each GraphQL execution.  For WebSocket requests, the same user
context instance is passed to each GraphQL subscription and data event resolver execution.

As such, do not create objects within the user context that rely on having the same
dependency injection service scope as the field resolvers.  Since WebSocket connections
are long-lived, using scoped services within a user context builder will result in those
scoped services having a matching long lifetime.  You may wish to alleviate this by
creating a service scope temporarily within your user context builder.

For applications that service multiple schemas, you may register `IUserContextBuilder<TSchema>`
to create a user context for a specific schema.  This is useful when you need to create
a user context that is specific to a particular schema.

### Mutations within GET requests

For security reasons and pursuant to current recommendations, mutation GraphQL requests
are rejected over HTTP GET connections.  Derive from `GraphQLHttpMiddleware<T>` and override
`ExecuteRequestAsync` to prevent injection of the validation rules that enforce this behavior.

As would be expected, subscription requests are only allowed over WebSocket channels.

### Handling form data for POST requests

The GraphQL over HTTP specification does not outline a procedure for transmitting GraphQL requests via
HTTP POST connections using a `Content-Type` of `application/x-www-form-urlencoded` or `multipart/form-data`.
Allowing the processing of such requests could be advantageous in avoiding CORS preflight requests when
sending GraphQL queries from a web browser.  Nevertheless, enabling this feature may give rise to security
risks when utilizing cookie authentication, since transmitting cookies with these requests does not trigger
a pre-flight CORS check.  As a consequence, GraphQL.NET might execute a request and potentially modify data
even when the CORS policy prohibits it, regardless of whether the sender has access to the response.
This situation exposes the system to security vulnerabilities, which should be carefully evaluated and
mitigated to ensure the safe handling of GraphQL requests and maintain the integrity of the data.

To mitigate this potential security vulnerability, CSRF protection is enabled by default, requiring a
`GraphQL-Require-Preflight` header to be sent with form data requests, which will trigger a CORS preflight
request.  In addition, form data requests are disabled by default, as they are not recommended for typical
use.

To enable form data for POST request, set the `ReadFormOnPost` setting to `true`.  GraphQL.NET Server supports
two formats of `application/x-www-form-urlencoded` or `multipart/form-data` requests:

1. The following keys are read from the form data and used to populate the GraphQL request:
   - `query`: The GraphQL query string.
   - `operationName`: The name of the operation to execute.
   - `variables`: A JSON-encoded object containing the variables for the operation.
   - `extensions`: A JSON-encoded object containing the extensions for the operation.

2. The following keys are read from the form data and used to populate the GraphQL request:
   - `operations`: A JSON-encoded object containing the GraphQL request, in the same format as typical
     requests sent via `application/json`.  This can be a single object or an array of objects if batching
     is enabled.
   - `map`: An optional JSON-encoded map of file keys to file objects.  This is used to map attached files
     into the GraphQL request's variables property.  See the section below titled 'File uploading/downloading' and the
     [GraphQL multipart request specification](https://github.com/jaydenseric/graphql-multipart-request-spec)
     for additional details.  Since `application/x-www-form-urlencoded` cannot transmit files, this feature
     is only available for `multipart/form-data` requests.

### Excessive `OperationCanceledException`s

When hosting a WebSockets endpoint, it may be common for clients to simply disconnect rather
than gracefully terminating the connection — most specifically when the client is a web browser.
If you log exceptions, you may notice an `OperationCanceledException` logged any time this occurs.

In some scenarios you may wish to log these exceptions — for instance, when the GraphQL endpoint is
used in server-to-server communications — but if you wish to ignore these exceptions, simply call
`app.UseIgnoreDisconnections();` immediately after any exception handling or logging configuration calls.
This will consume any `OperationCanceledException`s when `HttpContext.RequestAborted` is signaled — for
a WebSocket request or any other request.

```csharp
var app = builder.Build();
app.UseDeveloperExceptionPage();
app.UseIgnoreDisconnections();
app.UseWebSockets();
app.UseGraphQL();
```

### File uploading/downloading

A common question is how to upload or download files attached to GraphQL data.
For instance, storing and retrieving photographs attached to product data.

One common technique is to encode the data as Base64 and transmitting as a custom
GraphQL scalar (encoded as a string value within the JSON transport).
This may not be ideal, but works well for smaller files.  It can also couple with
response compression (details listed above) to reduce the impact of the Base64
encoding.

Another technique is to get or store the data out-of-band.  For responses, this can
be as simple as a Uri pointing to a location to retrieve the data, especially if
the data are photographs used in a SPA client application.  This may have additional
security complications, especially when used with JWT bearer authentication.
This answer often works well for GraphQL queries, but may not be desired during
uploads (mutations).

An option for uploading is to upload file data alongside a mutation with the
`multipart/form-data` content type as described by the
[GraphQL multipart request specification](https://github.com/jaydenseric/graphql-multipart-request-spec).
Uploaded files are mapped into the GraphQL request's variables as `IFormFile` objects.
You can use the provided `FormFileGraphType` scalar graph type in your GraphQL schema
to access these files.  The `AddFormFileGraphType()` builder extension method adds this scalar
to the DI container and configures a CLR type mapping for it to be used for `IFormFile` objects.

```csharp
services.AddGraphQL(b => b
    .AddAutoSchema<Query>()
    .AddFormFileGraphType()
    .AddSystemTextJson());
```

Please see the 'Upload' sample for a demonstration of this technique, which also
demonstrates the use of the `MediaTypeAttribute` to restrict the allowable media
types that will be accepted.  Note that using the `FormFileGraphType` scalar requires
that the uploaded files be sent only via the `multipart/form-data` content type as
attached files, with the `ReadFormOnPost` option enabled. If you also wish to allow
clients to send files as base-64 encoded strings, you can write a custom scalar
better suited to your needs.

### Native AOT support

GraphQL.NET Server fully supports Native AOT publishing with .NET 8.0 and later.
See [ASP.NET Core support for Native AOT](https://learn.microsoft.com/en-us/aspnet/core/fundamentals/native-aot)
for a list of features supported by .NET 8.0.  However, GraphQL.NET only provides limited
support for Native AOT publishing due to its extensive use of reflection.  Please see
[GraphQL.NET Ahead-of-time compilation](https://github.com/graphql-dotnet/graphql-dotnet?tab=readme-ov-file#ahead-of-time-compilation)
for more information.

## Samples

The following samples are provided to show how to integrate this project with various
typical ASP.NET Core scenarios.

| Name            | Framework                | Description |
|-----------------|--------------------------|-------------|
| Authorization   | .NET 8 Minimal           | Based on the VS template, demonstrates authorization functionality with cookie-based authentication |
| Basic           | .NET 8 Minimal           | Demonstrates simplest possible implementation |
| Complex         | .NET 3.1 / 6 / 8         | Demonstrates older Program/Startup files and various configuration options, and multiple UI endpoints |
| Controller      | .NET 8 Minimal           | MVC implementation; does not include WebSocket support |
| Cors            | .NET 8 Minimal           | Demonstrates configuring a GraphQL endpoint to use a specified CORS policy |
| EndpointRouting | .NET 8 Minimal           | Demonstrates configuring GraphQL through endpoint routing |
| HttpResult      | .NET 8 Minimal           | Demonstrates using `MapGet` and/or `MapPost` to return a GraphQL response |
| Jwt             | .NET 8 Minimal           | Demonstrates authenticating GraphQL requests with a JWT bearer token over HTTP POST and WebSocket connections |
| MultipleSchemas | .NET 8 Minimal           | Demonstrates configuring multiple schemas within a single server |
| NativeAot       | .NET 8 Slim              | Demonstrates configuring GraphQL for Native AOT publishing |
| Net48           | .NET Core 2.1 / .NET 4.8 | Demonstrates configuring GraphQL on .NET 4.8 / Core 2.1 |
| Pages           | .NET 8 Minimal           | Demonstrates configuring GraphQL on top of a Razor Pages template |
| Upload          | .NET 8 Minimal           | Demonstrates uploading files via the `multipart/form-data` content type |

Most of the above samples rely on a sample "Chat" schema.
Below are some basic requests you can use to test the schema:

### Queries

#### Return number of messages

```graphql
{
  count
}
```

#### Return last message

```graphql
{
  lastMessage {
    id
    message
    from
    sent
  }
}
```

### Mutations

#### Add a message

```graphql
mutation {
  addMessage(message: { message: "Hello", from: "John Doe" }) {
    id
  }
}
```

#### Clear all messages

```graphql
mutation {
  clearMessages
}
```

### Subscriptions

```graphql
subscription {
  newMessages {
    id
    message
    from
    sent
  }
}
```

## Contributors

This project exists thanks to all the people who contribute. 
<a href="https://github.com/graphql-dotnet/server/graphs/contributors"><img src="https://contributors-img.web.app/image?repo=graphql-dotnet/server" /></a>

PRs are welcome! Looking for something to work on? The list of [open issues](https://github.com/graphql-dotnet/server/issues)
is a great place to start. You can help the project by simply responding to some of the [asked questions](https://github.com/graphql-dotnet/server/issues?q=is%3Aissue+is%3Aopen+label%3Aquestion).

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