ZeroQL |

C# GraphQL client with Linq-like syntax

Description

The ZeroQL is a high-performance C#-friendly GraphQL client. It supports Linq-like syntax. It doesn't require Reflection.Emit or expressions. As a result, the runtime provides performance very close to a raw HTTP call.

There is a more detailed list of what the ZeroQL can do at the moment:

Programming language: C#

License: MIT License

Tags: Csharp     Performance     Client     GraphQL    

README

ZeroQL |

The ZeroQL is a high-performance C#-friendly GraphQL client. It supports Linq-like syntax. It does't not require Reflection.Emit or expressions. As a result, in runtime provides performance very close to a raw HTTP call.

There is a more detailed list of what the ZeroQL can do at the moment:

• [ ] Bootstrap schema.graphql file from graphql endpoint
• [x] Bootstrap client from schema.graphql file
• [x] Support for queries and mutations
  • [x] "Lambda" like syntax
  • [x] "Request" like syntax
• [ ] Support for subscriptions
• [x] Support for fragments
• [x] Support for file uploads
• [x] Support for persisted queries
• [x] Support for user defined scalars
• [ ] Support for @defer
• [ ] Support for @stream

The articles:

• ZeroQL - C# friendly graphql client
• ZeroQL - C# GraphQL client adds fragments support
• ZeroQL V2 - C# GraphQL client

How to setup

The initial setup:

# create console app
dotnet new console -o QLClient
# go to project folder 
cd QLClient
# fetch graphql schema from server(depends on your web server)
curl http://localhost:10000/graphql?sdl > schema.graphql 
# create manifest file to track nuget tools
dotnet new tool-manifest 
# add ZeroQL.CLI nuget tool
dotnet tool install ZeroQL.CLI
# add ZeroQL nuget package
dotnet add package ZeroQL 
# to bootstrap schema.graphql file from graphql schema
dotnet zeroql generate --schema .\schema.graphql --namespace TestServer.Client --client-name TestServerGraphQLClient --output Generated/GraphQL.g.cs

It is possible to add next target to csproj to keep generated client in sync with schema.graphql:

<Target Name="GenerateQLClient" BeforeTargets="BeforeCompile">
    <Exec Command="dotnet zeroql generate --schema .\schema.graphql --namespace TestServer.Client --client-name TestServerGraphQLClient --output Generated/GraphQL.g.cs" />
</Target>

As a result, the graphql client will be generated on every build.

How to use

Let's suppose that schema.graphql file contains the following:

schema {
  query: Queries
  mutation: Mutation
}

type Queries {
  me: User!
  user(id: Int!): User
}

type Mutation {
  addUser(firstName: String!, lastName: String!): User!
  addUserProfileImage(userId: Int! file: Upload!): Int!
}

type User {
  id: Int!
  firstName: String!
  lastName: String!
  role: Role!
}

type Role {
  id: Int!
  name: String!
}

and we want to execute the query like that:

query { me { id firstName lastName } }

GraphQL lambda syntax

Here how we can achieve it with ZeroQL "lambda" syntax:

var httpClient = new HttpClient();
httpClient.BaseAddress = new Uri("http://localhost:10000/graphql");

var client = new TestServerGraphQLClient(httpClient);

var response = await client.Query(static o => o.Me(o => new { o.Id, o.FirstName, o.LastName }));

Console.WriteLine($"GraphQL: {response.Query}"); // GraphQL: query { me { id firstName lastName } }
Console.WriteLine($"{response.Data.Id}: {response.Data.FirstName} {response.Data.LastName}"); // 1: Jon Smith

You can pass arguments if needed:

var variables = new { Id = 1 };
var response = await client.Query(variables, static (i, o) => o.User(i.Id, o => new { o.Id, o.FirstName, o.LastName }));

Console.WriteLine($"GraphQL: {response.Query}"); // GraphQL: query ($id: Int!) { user(id: $id) { id firstName lastName } }
Console.WriteLine($"{response.Data.Id}: {response.Data.FirstName} {response.Data.LastName}"); // 1: Jon Smith

You can fetch attached fields:

var variables = new { Id = 1 };
var response = await client.Query(
    variables,
    static (i, o) => o
        .User(i.Id,
            o => new
            {
                o.Id,
                o.FirstName,
                o.LastName,
                Role = o.Role(role => role.Name)
            }));

Console.WriteLine($"GraphQL: {response.Query}"); // GraphQL: query GetUserWithRole($id: Int!) { user(id: $id) { id firstName lastName role { name }  } }
Console.WriteLine($"{response.Data.Id}: {response.Data.FirstName} {response.Data.LastName}, Role: {response.Data.Role}"); // 1: Jon Smith, Role: Admin

GraphQL request syntax

In more complex queries, the "lambda" syntax may look verbose, and extracting requests into a separate entity would be nice. Now it is possible to do it via the "request" syntax. Here is an example:

// define a request
public record GetUserQuery(int Id) : GraphQL<Queries, UserModel?>
{
    public override UserModel? Execute(Queries query) 
        => query.User(Id, o => new UserModel(o.Id, o.FirstName, o.LastName));
}

// execute a request
var response = await client.Execute(new GetUserQuery(variables.FriendId));

Console.WriteLine(response.Query); // query GetUserQuery($id: Int!) { user(id: $id) { id firstName lastName } }
Console.WriteLine(response.Data); // UserModel { Id = 2, FirstName = Ben, LastName = Smith }

You need to create a record from the base record GraphQL<TOperationType, TResult>. Where the TOperationType is a root query type(Query, Mutation) that associated with the GraphQLClient<TQuery, TMutataion> instance.

Fragments

It is possible to define and reuse fragments:

public static class UserFragments
{
    [GraphQLFragment]
    public static UserDetails ToUserDetails(this User user)
    {
        return new UserDetails
        {
            Id = user.Id,
            FirstName = user.FirstName,
            LastName = user.LastName
        };
    }
}

var variables = new { Id = 1 };
var response = await client.Query(
    variables,
    static (i, q) => 
        new 
        { 
            Me = q.Me(o => o.ToUserDetails()),
            User = q.User(i.Id, o => o.ToUserDetails())
        });


Console.WriteLine($"GraphQL: {response.Query}"); // GraphQL: query ($id: Int!) { me { id firstName lastName } user(id: $id) { id firstName lastName } }
Console.WriteLine($"{response.Data.Me.Id}: {response.Data.Me.FirstName} {response.Data.Me.LastName}"); // 1: Jon Smith
Console.WriteLine($"{response.Data.User.Id}: {response.Data.User.FirstName} {response.Data.User.LastName}"); // 1: Jon Smith

The fragment should be marked with the [GraphQLFragment] attribute, and it should be an extension method. If the fragment is defined in another assembly, it should be a partial method. The last requirement is necessary because source generators don't have access to source code from another assembly. So, a workaround will be to define fragments as a partial method and generate additional metadata.

File upload

The ZeroQL supports file uploading via the "official" GraphQL way - the Upload type. There is an example:

public record AddAvatar(int Id, Upload File) : GraphQL<Mutation, int>
{
    public override int Execute(Mutation mutation)
        => mutation.AddUserProfileImage(Id, File);
}

There is one nuance associated with the Upload type. Pay attention to how you pass the Upload instance. For example, if it is a anonymous type new { File = new Upload("image.png", new MemoryStream()) } that means that reflection is going to be utilized to get the value. As a result, the Reflection.Emit is involved, which can be an issue in AOT scenarios. So, the "request" syntax would be better for such a case.

Persisted queries

To use persisted queries, we need to pass PersistedQueryPipeline inside GraphQLClient:

var client = new TestServerGraphQLClient(httpClient, new PersistedQueryPipeline()); 
var response = await client.Execute(new GetUserQuery(1)); 

Console.WriteLine($"GraphQL: {response.Query}"); // GraphQL: 8cc1ee42eecdac2a8590486826856c041b04981a2c55d5cc560c338e1f6f0285:query GetUserQuery($id: Int!) { user(id: $id) { id firstName lastName } }
Console.WriteLine(response.Data); // UserModel { Id = 1, FirstName = Jon, LastName = Smith }

Now the client will follow "automatic persisted queries" pipeline. Description is here here.

When we need the "persisted queries" pipeline, described here, then change the client initialization like that:

var client = new TestServerGraphQLClient(httpClient, new PersistedQueryPipeline(tryToAddPersistedQueryOnFail: false));

and export defined queries from the assembly:

 dotnet zeroql queries extract -a .\bin\Debug\net6.0\TestProject.dll -c TestServer.Client.TestServerGraphQLClient -o ./queries

The queries folder will contain the set of the "hashed" GraphQL files that you need for your GraphQL server setup:

8cc1ee42eecdac2a8590486826856c041b04981a2c55d5cc560c338e1f6f0285.graphql # query GetUserQuery($id: Int!) { user(id: $id) { id firstName lastName } }
21cc96eaf0c0db2b5f980c8ec8b5aba2e40eb24f370cfc0cd7e4825509742ae2.graphql # mutation AddAvatar($id: Int!, $file: Upload!) { addUserProfileImage(userId: $id, file: $file)}

User defined scalars

Let's suppose that server returns the Instant type from NodaTime. The schema looks like that

"""
Represents an instant on the global timeline, with nanosecond resolution.
"""
scalar Instant

type Query {
  instant: Instant!
}

The ZeroQL knows nothing about the scalar type Instant, but we should be able to add support for it. To make it work, create the class Instant in the ZeroQL namespace and define a JSON serializer for it:

namespace ZeroQL;

public class Instant
{
    public DateTimeOffset DateTimeOffset { get; set; }
}

public class InstantJsonConverter : JsonConverter<Instant?>
{
    public override Instant? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        var text = reader.GetString();
        if (string.IsNullOrEmpty(text))
        {
            return null;
        }
        return new Instant { DateTimeOffset = DateTimeOffset.Parse(text) };
    }

    public override void Write(Utf8JsonWriter writer, Instant? value, JsonSerializerOptions options)
    {
        var text = value?.DateTimeOffset.ToString("O");
        writer.WriteStringValue(text);
    }
}

Then, somewhere in your app, add this serializer to JSON options:

ZeroQLJsonOptions.Configure(o => o.Converters.Add(new InstantJsonConverter()));

Now we are ready to consume it:

var response = await qlClient.Query(static q => q.Instant);

Benchmarks

The complete benchmark source code you can find here.

The short version looks like this:

[Benchmark]
public async Task<string> Raw()
{
    var rawQuery = @"{ ""query"": ""query { me { firstName }}"" }";
    var response = await httpClient.PostAsync("", new StringContent(rawQuery, Encoding.UTF8, "application/json"));
    var responseJson = await response.Content.ReadAsStreamAsync();
    var qlResponse = JsonSerializer.Deserialize<JsonObject>(responseJson, options);

    return qlResponse["data"]["me"]["firstName"].GetValue<string>();
}

[Benchmark]
public async Task<string> StrawberryShake()
{
    var firstname = await strawberryShake.Me.ExecuteAsync();
    return firstname.Data.Me.FirstName;
}

[Benchmark]
public async Task<string> ZeroQL()
{
    var firstname = await zeroQLClient.Query(static q => q.Me(o => o.FirstName));

    return firstname.Data;
}

Here results:

BenchmarkDotNet=v0.13.1, OS=macOS Monterey 12.5.1 (21G83) [Darwin 21.6.0]
Apple M1, 1 CPU, 8 logical and 8 physical cores
.NET SDK=6.0.400
  [Host]     : .NET 6.0.8 (6.0.822.36306), Arm64 RyuJIT
  DefaultJob : .NET 6.0.8 (6.0.822.36306), Arm64 RyuJIT

Method	Mean	Error	StdDev	Gen 0	Allocated
Raw	186.0 μs	1.08 μs	1.01 μs	2.4414	5 KB
StrawberryShake	193.8 μs	1.28 μs	1.20 μs	3.1738	6 KB
ZeroQLLambda	187.5 μs	1.23 μs	1.09 μs	2.6855	6 KB
ZeroQLRequest	188.2 μs	0.83 μs	0.74 μs	2.9297	6 KB

As you can see, the Raw method is the fastest. The ZeroQL method is a bit faster than the StrawberryShake method. But in absolute terms, all of them are pretty much the same.

So, with the ZeroQL you can forget about the graphql and just use the Linq-like interface. It will have little effect on performace.