GraphQL.Server.Transports.AspNetCore 7.6.0

ASP.NET Core GraphQL Server driven by GraphQL.NET

GraphQL ASP.NET Core server on top of GraphQL.NET. HTTP transport compatible with the GraphQL over HTTP draft specification. WebSocket transport compatible with both subscriptions-transport-ws and 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			Includes all the packages below, excluding the legacy authorization package, plus the GraphQL.DataLoader and GraphQL.MemoryCache packages
GraphQL.Server.Authorization.AspNetCore (deprecated)			Provides legacy authorization rule support (deprecated; please use GraphQL.Server.Transports.AspNetCore)
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			Provides Altair UI middleware
GraphQL.Server.Ui.Playground			Provides Playground UI middleware
GraphQL.Server.Ui.GraphiQL			Provides GraphiQL UI middleware
GraphQL.Server.Ui.Voyager			Provides Voyager UI middleware

You can install the latest stable versions via NuGet. Also you can get all preview versions from GitHub Packages. Note that GitHub requires authentication to consume the feed. See more information here.

⚠️ When upgrading from prior versions, please remove references to these old packages ⚠️
GraphQL.Server.Core
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 6.0) 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. WebSocket requests can use the graphql-ws or graphql-transport-ws WebSocket sub-protocol, as defined in the apollographql/subscriptions-transport-ws and enisdenjo/graphql-ws repositories, respectively.

The middleware can be configured through the IApplicationBuilder or IEndpointRouteBuilder builder interfaces. In addition, an ExecutionResultActionResult class is added for returning ExecutionResult instances directly from a controller action.

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.

See migration notes for changes from version 6.x.

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 7.0.0 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 UseGraphQLVoyager 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

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

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

  <ItemGroup>
    <PackageReference Include="GraphQL.Server.All" Version="7.0.0" />
  </ItemGroup>

</Project>

Program.cs file

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.UseGraphQLPlayground(
    "/",                               // url to host Playground at
    new GraphQL.Server.Ui.Playground.PlaygroundOptions
    {
        GraphQLEndPoint = "/graphql",         // url of GraphQL endpoint
        SubscriptionsEndPoint = "/graphql",   // url of GraphQL endpoint
    });
await app.RunAsync();

Schema

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

Sample request url

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

Sample response

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

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:

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:

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

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

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.

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:

[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:

[FunctionName("Playground")]
public static IActionResult RunGraphQL(
    [HttpTrigger(AuthorizationLevel.Anonymous, "get"] HttpRequest req)
{
    return new PlaygroundActionResult(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

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

MyUserContext.cs

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:

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.

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:

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 be returned to unauthenticated users within an graph that has an authorization requirement defined.

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:

{
  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.

⚠️ Note that authorization rules are ignored for input types and fields of input types ⚠️

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:

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:

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. See review the following methods for configuration options within each of the 4 respective NuGet packages:

app.UseGraphQLAltair();
app.UseGraphQLGraphiQL();
app.UseGraphQLPlayground();
app.UseGraphQLVoyager();

// or

endpoints.MapGraphQLAltair();
endpoints.MapGraphQLGraphiQL();
endpoints.MapGraphQLPlayground();
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.

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.

// ...
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();

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:

// add and configure the service
builder.Services.AddResponseCompression(options =>
{
    options.EnableForHttps = true; // may lead to CRIME and BREACH attacks
    options.MimeTypes = new[] { "application/json", "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 and this 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:

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.
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
ReadExtensionsFromQueryString	Enables reading extensions from the query string.	True
ReadFormOnPost	Enables parsing of form data for POST requests (may have security implications).	True
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.	True
WebSockets	Returns a set of configuration properties for WebSocket connections.

GraphQLWebSocketOptions

Property	Description	Default value
ConnectionInitWaitTimeout	The amount of time to wait for a GraphQL initialization packet before the connection is closed.	10 seconds
KeepAliveTimeout	The amount of time to wait between sending keep-alive packets.	disabled
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

Multi-schema configuration

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

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.

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:

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
    }
}

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:

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:

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.

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.

This functionality is activated by default to maintain backward compatibility, but it can be turned off by setting the ReadFormOnPost value to false. The next major version of GraphQL.NET Server will have this feature disabled by default, enhancing security measures.

Keep in mind that CORS pre-flight requests are also not executed for GET requests, potentially presenting a security risk. However, GraphQL query operations usually do not alter data, and mutations are refused. Additionally, the response is not expected to be readable in the browser (unless CORS checks are successful), which helps alleviate this concern.

Excessive OperationCanceledExceptions

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 OperationCanceledExceptions when HttpContext.RequestAborted is signaled — for a WebSocket request or any other request.

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. Please see Issue 307 and FileUploadTests.cs for discussion and demonstration of this capability.

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 6 Minimal	Based on the VS template, demonstrates authorization functionality with cookie-based authentication
Basic	.NET 6 Minimal	Demonstrates simplest possible implementation
Complex	.NET 3.1 / 5 / 6	Demonstrates older Program/Startup files and various configuration options, and multiple UI endpoints
Controller	.NET 6 Minimal	MVC implementation; does not include WebSocket support
Cors	.NET 6 Minimal	Demonstrates configuring a GraphQL endpoint to use a specified CORS policy
EndpointRouting	.NET 6 Minimal	Demonstrates configuring GraphQL through endpoint routing
Jwt	.NET 6 Minimal	Demonstrates authenticating GraphQL requests with a JWT bearer token over HTTP POST and WebSocket connections
MultipleSchemas	.NET 6 Minimal	Demonstrates configuring multiple schemas within a single server
Net48	.NET Core 2.1 / .NET 4.8	Demonstrates configuring GraphQL on .NET 4.8 / Core 2.1
Pages	.NET 6 Minimal	Demonstrates configuring GraphQL on top of a Razor Pages template

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

{
  count
}

Return last message

{
  lastMessage {
    id
    message
    from
    sent
  }
}

Mutations

Add a message

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

Clear all messages

mutation {
  clearMessages
}

Subscriptions

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 is a great place to start. You can help the project by simply responding to some of the asked questions.