GraphQL C# client generator

This simple console app generates C# GraphQL query builder and data classes for simple, compiler checked, usage of a GraphQL API.

Generator app usage

GraphQlClientGenerator.Console --serviceUrl <GraphQlServiceUrl> --outputPath <TargetPath> --namespace <TargetNamespace> [--header <header value>]

Nuget package

Installation:

Install-Package GraphQlClientGenerator

dotnet tool

dotnet tool install GraphQlClientGenerator.Tool --global
graphql-client-generator --serviceUrl <GraphQlServiceUrl> --outputPath <TargetPath> --namespace <TargetNamespace> [--header <header value>]

Code

Code example for class generation:

var schema = await GraphQlGenerator.RetrieveSchema(url);
var generator = new GraphQlGenerator();
var generatedClasses = generator.GenerateFullClientCSharpFile(schema);

or using full blown setup:

var schema = await GraphQlGenerator.RetrieveSchema(url);
var builder = new StringBuilder();
using var writer = new StringWriter(builder);
var generationContext = new SingleFileGenerationContext(schema, writer) { LogMessage = Console.WriteLine };
var configuration = new GraphQlGeneratorConfiguration { TargetNamespace = "MyGqlApiClient", ... };
var generator = new GraphQlGenerator(configuration);
generator.Generate(generationContext);
var csharpCode = builder.ToString();

C# 9 source generator

C# 9 introduced source generators that can be attached to compilation process. Generated classes will be automatically included in project.

Project file example:

<PropertyGroup>
  <OutputType>Exe</OutputType>
  <TargetFramework>net5.0</TargetFramework>

  <!-- GraphQL generator properties -->
  <GraphQlClientGenerator_ServiceUrl>https://api.tibber.com/v1-beta/gql</GraphQlClientGenerator_ServiceUrl>
  <!-- GraphQlClientGenerator_Namespace is optional; if omitted the first compilation unit namespace will be used -->
  <GraphQlClientGenerator_Namespace>$(RootNamespace)</GraphQlClientGenerator_Namespace>
  <GraphQlClientGenerator_CustomClassMapping>Consumption:ConsumptionEntry|Production:ProductionEntry|RootMutation:TibberMutation|Query:Tibber</GraphQlClientGenerator_CustomClassMapping>
  
  <!-- other GraphQL generator property values -->
  
</PropertyGroup>

<ItemGroup>
  <PackageReference Include="GraphQlClientGenerator" Version="0.9.*" IncludeAssets="analyzers" />
  
  <!-- AdditionalFiles and GraphQlClientGenerator_ServiceUrl are mutually exclusive -->
  <!-- <AdditionalFiles Include="GqlSchemaTibberApi.gql.schema.json" CacheObjects="true" /> --> <!-- schema file name must end with ".gql.schema.json" -->
  
  <CompilerVisibleProperty Include="GraphQlClientGenerator_ServiceUrl" />
  <CompilerVisibleProperty Include="GraphQlClientGenerator_Namespace" />
  <!-- other configuration properties -->
  <!--<CompilerVisibleProperty Include="GraphQlClientGenerator_{ConfigurationProperty}" />-->
</ItemGroup>

Query builder usage

var builder =
  new QueryQueryBuilder()
    .WithMe(
      new MeQueryBuilder()
        .WithAllScalarFields()
        .WithHome(
          new HomeQueryBuilder()
            .WithAllScalarFields()
            .WithSubscription(
              new SubscriptionQueryBuilder()
                .WithStatus()
                .WithValidFrom())
            .WithSignupStatus(
              new SignupStatusQueryBuilder().WithAllFields())
            .WithDisaggregation(
              new DisaggregationQueryBuilder().WithAllFields()),
          "b420001d-189b-44c0-a3d5-d62452bfdd42")
        .WithEnergyStatements ("2016-06", "2016-10"));

var query = builder.Build(Formatting.Indented);

results into

query {
  me {
    id
    firstName
    lastName
    fullName
    ssn
    email
    language
    tone
    home (id: "b420001d-189b-44c0-a3d5-d62452bfdd42") {
      id
      avatar
      timeZone
      subscription {
        status
        validFrom
      }
      signupStatus {
        registrationStartedTimestamp
        registrationCompleted
        registrationCompletedTimestamp
        checkCurrentSupplierPassed
        supplierSwitchConfirmationPassed
        startDatePassed
        firstReadingReceived
        firstBillingDone
        firstBillingTimestamp
      }
      disaggregation {
        year
        month
        fixedConsumptionKwh
        fixedConsumptionKwhPercent
        heatingConsumptionKwh
        heatingConsumptionKwhPercent
        behaviorConsumptionKwh
        behaviorConsumptionKwhPercent
      }
    }
    energyStatements(from: "2016-06", to: "2016-10") 
  }
}

Mutation

var mutation =
  new MutationQueryBuilder()
    .WithUpdateHome(
      new HomeQueryBuilder().WithAllScalarFields(),
      new UpdateHomeInput { HomeId = Guid.Empty, AppNickname = "My nickname", Type = HomeType.House, NumberOfResidents = 4, Size = 160, AppAvatar = HomeAvatar.Floorhouse1, PrimaryHeatingSource = HeatingSource.Electricity }
    )
    .Build(Formatting.Indented, 2);

result:

mutation {
  updateHome (input: {
      homeId: "00000000-0000-0000-0000-000000000000"
      appNickname: "My nickname"
      appAvatar: FLOORHOUSE1
      size: 160
      type: HOUSE
      numberOfResidents: 4
      primaryHeatingSource: ELECTRICITY
    }) {
    id
    timeZone
    appNickname
    appAvatar
    size
    type
    numberOfResidents
    primaryHeatingSource
    hasVentilationSystem
  }
}

Field exclusion

Sometimes there is a need to select almost all fields of a queried object except few. In that case Except methods can be used often in conjunction with WithAllFields or WithAllScalarFields.

new ViewerQueryBuilder()
  .WithHomes(
    new HomeQueryBuilder()
      .WithAllScalarFields()
      .ExceptPrimaryHeatingSource()
      .ExceptMainFuseSize()
  )
  .Build(Formatting.Indented);

result:

query {
  homes {
    id
    timeZone
    appNickname
    appAvatar
    size
    type
    numberOfResidents
    hasVentilationSystem
  }
}

Aliases

Queried fields can be freely renamed to match target data classes using GraphQL aliases.

new ViewerQueryBuilder("MyQuery")
  .WithHome(
    new HomeQueryBuilder()
      .WithType()
      .WithSize()
      .WithAddress(new AddressQueryBuilder().WithAddress1("primaryAddressText").WithCountry(), "primaryAddress"),
    Guid.NewGuid(),
    "primaryHome")
  .WithHome(
    new HomeQueryBuilder()
      .WithType()
      .WithSize()
      .WithAddress(new AddressQueryBuilder().WithAddress1("secondaryAddressText").WithCountry(), "secondaryAddress"),
    Guid.NewGuid(),
    "secondaryHome")
  .Build(Formatting.Indented);

result:

query MyQuery {
  primaryHome: home (id: "120efe4a-6839-45fc-beed-27455d29212f") {
    type
    size
    primaryAddress: address {
      primaryAddressText: address1
      country
    }
  }
  secondaryHome: home (id: "0c735830-be56-4a3d-a8cb-d0189037f221") {
    type
    size
    secondaryAddress: address {
      secondaryAddressText: address1
      country
    }
  }
}

Query parameters

var homeIdParameter = new GraphQlQueryParameter<Guid>("homeId", "ID", homeId);

var builder =
  new TibberQueryBuilder()
    .WithViewer(
      new ViewerQueryBuilder()
        .WithHome(new HomeQueryBuilder().WithAllScalarFields(), homeIdParameter)
    )
    .WithParameter(homeIdParameter);

result:

query ($homeId: ID = "c70dcbe5-4485-4821-933d-a8a86452737b") {
  viewer{
    home(id: $homeId) {
      id
      timeZone
      appNickname
      appAvatar
      size
      type
      numberOfResidents
      primaryHeatingSource
      hasVentilationSystem
      mainFuseSize
    }
  }
}

Directives

var includeDirectParameter = new GraphQlQueryParameter<bool>("direct", "Boolean", true);
var includeDirective = new IncludeDirective(includeDirectParameter);
var skipDirective = new SkipDirective(true);

var builder =
  new TibberQueryBuilder()
    .WithViewer(
       new ViewerQueryBuilder()
         .WithName(include: includeDirective)
         .WithAccountType(skip: skipDirective)
         .WithHomes(new HomeQueryBuilder().WithId(), skip: skipDirective)
    )
    .WithParameter(includeDirectParameter);

result:

query (
  $direct: Boolean = true) {
  viewer {
    name @include(if: $direct)
    accountType @skip(if: true)
    homes @skip(if: true) {
      id
    }
  }
}

Inline fragments

var builder =
  new RootQueryBuilder("InlineFragments")
    .WithUnion(
      new UnionTypeQueryBuilder()
        .WithTypeName()
        .WithConcreteType1Fragment(new ConcreteType1QueryBuilder().WithAllFields())
        .WithConcreteType2Fragment(new ConcreteType2QueryBuilder().WithAllFields())
        .WithConcreteType3Fragment(
          new ConcreteType3QueryBuilder()
            .WithTypeName()
            .WithName()
            .WithConcreteType3Field("alias")
            .WithFunction("my value", "myResult1")
        )
    )
    .WithInterface(
      new NamedTypeQueryBuilder()
        .WithName()
        .WithConcreteType3Fragment(
          new ConcreteType3QueryBuilder()
            .WithTypeName()
            .WithName()
            .WithConcreteType3Field()
            .WithFunction("my value")
        ),
      Guid.Empty
    );

result:

query InlineFragments {
  union {
    __typename
    ... on ConcreteType1 {
      name
      concreteType1Field
    }
    ... on ConcreteType2 {
      name
      concreteType2Field
    }
    ... on ConcreteType3 {
      __typename
      name
      alias: concreteType3Field
      myResult1: function(value: "my value")
    }
  }
  interface(parameter: "00000000-0000-0000-0000-000000000000") {
    name
    ... on ConcreteType3 {
      __typename
      name
      concreteType3Field
      function(value: "my value")
    }
  }
}

Custom scalar types

GraphQL supports custom scalar types. By default these are mapped to object type. To ensure appropriate .NET types are generated for data class properties custom mapping interface can be used:

var configuration = new GraphQlGeneratorConfiguration();
configuration.ScalarFieldTypeMappingProvider = new MyCustomScalarFieldTypeMappingProvider();

public class MyCustomScalarFieldTypeMappingProvider : IScalarFieldTypeMappingProvider
{
    public ScalarFieldTypeDescription GetCustomScalarFieldType(GraphQlGeneratorConfiguration configuration, GraphQlType baseType, GraphQlTypeBase valueType, string valueName)
    {
        valueType = valueType is GraphQlFieldType fieldType ? fieldType.UnwrapIfNonNull() : valueType;

        // DateTime and Byte
        switch (valueType.Name)
        {
            case "Byte": return new ScalarFieldTypeDescription { NetTypeName = "byte?", FormatMask = null };
            case "DateTime": return new ScalarFieldTypeDescription { NetTypeName = "DateTime?", FormatMask = null };
        }

        // fallback - not needed if all fields and arguments are resolved or the expected type is of "object" type
        return DefaultScalarFieldTypeMappingProvider.GetFallbackFieldType(configuration, valueType);
    }
}

Generated class example:

public class OrderType
{
    public DateTime? CreatedDateTimeUtc { get; set; }
    public byte? SomeSmallNumber { get; set; }
}

vs.

public class OrderType
{
    public object CreatedDateTimeUtc { get; set; }
    public object SomeSmallNumber { get; set; }
}

C# 9 source generator custom types

Source generator supports RegexScalarFieldTypeMappingProvider rules using JSON configuration file. Example:

[
  {
    "patternBaseType": ".+",
    "patternValueType": ".+",
    "patternValueName": "^((timestamp)|(.*(f|F)rom)|(.*(t|T)o))$",
    "netTypeName": "DateTimeOffset?",
    "formatMask": "O"
  }
]

All pattern values must be specified. Null values are not accepted.

The file must be named RegexScalarFieldTypeMappingProvider.gql.config.json and included as additional file.

<ItemGroup>
  <AdditionalFiles Include="RegexScalarFieldTypeMappingProvider.gql.config.json" CacheObjects="true" />
</ItemGroup>

Husqvik/GraphQlClientGenerator

GraphQL C# client generator

Generator app usage

Nuget package

dotnet tool

Code

C# 9 source generator

Query builder usage

Mutation

Field exclusion

Aliases

Query parameters

Directives

Inline fragments

Custom scalar types

C# 9 source generator custom types