TypedSignalR.Client.TypeScript

TypedSignalR.Client.TypeScript is a library/CLI tool that analyzes SignalR hub and receiver type definitions written in C# and generates TypeScript source code to provide strongly typed SignalR clients.

Table of Contents

• Why TypedSignalR.Client.TypeScript?
• Packages
  • Install Using .NET Tool
• Usage
• Supported Types
  • Built-in Supported Types
  • User Defined Types
• Analyzer
• Streaming Support
• Client Results Support
• MessagePack Hub Protocol Support
  • Default Configuration in ASP.NET Core
  • Recommended Configuration
• Related Work

Why TypedSignalR.Client.TypeScript?

Implementing SignalR Hubs (server-side) in C# can be strongly typed by using interfaces, but the TypeScript SignalR client is not strongly typed. To call Hub methods, we must specify the method defined in Hub using a string. We also have to determine the return type manually. Moreover, registering client methods called from a server also requires specifying the method name as a string, and we must set parameter types manually.

// TypeScript SignalR client
// without TypedSignalR.Client.TypeScript

// Specify a hub method to invoke using string.
await connection.invoke("HubMethod1");

// Manually determine a return type.
// Parameters are cast to any type.
const value = await connection.invoke<number>("HubMethod2", "message", 99);

// Registering a client method requires a string, and parameter types must be set manually.
const func = (message: string, count: number) => {...};
connection.on("ClientMethod", func);
connection.off("ClientMethod", func);

These are very painful and cause bugs.

TypedSignalR.Client.TypeScript aims to generates TypeScript source code to provide strongly typed SignalR clients by analyzing C# interfaces in which the server and client methods are defined. You only need to execute one command to analyze your C# code and generate TypeScript code. Please see the Install Using .NET Tool and Usage sections for more information.

$ dotnet tsrts --project path/to/Project.csproj --output generated

// TypeScript SignalR client
// with TypedSignalR.Client.TypeScript
// Generated source code

export type HubProxyFactory<T> = {
    createHubProxy(connection: HubConnection): T;
}

export type ReceiverRegister<T> = {
    register(connection: HubConnection, receiver: T): Disposable;
}

// Overload function type
// Because string literal types are used, there is no need to worry about typos.
export type HubProxyFactoryProvider = {
    // In this example, IHub1 and IHub2 are transpiled from C# to TypeScript.
    (hubType: "IHub1"): HubProxyFactory<IHub1>;
    (hubType: "IHub2"): HubProxyFactory<IHub2>;
}

// Overload function type
export type ReceiverRegisterProvider = {
    // In this example, IReceiver1 and IReceiver2 are transpiled from C# to TypeScript.
    (receiverType: "IReceiver1"): ReceiverRegister<IReceiver1>;
    (receiverType: "IReceiver2"): ReceiverRegister<IReceiver2>;
}

export const getHubProxyFactory : HubProxyFactoryProvider = ...; 
export const getReceiverRegister : ReceiverRegisterProvider = ...;

// Usage of generated code.

const hubProxy = getHubProxyFactory("IHub1") // HubProxyFactory<IHub1>
    .createHubProxy(connection); // IHub1

const receiver : IReceiver1 = {...};

const subscription = getReceiverRegister("IReceiver1") // ReceiverRegister<IReceiver1>
    .register(connection, receiver); // Disposable

// We no longer need to specify the method using a string.
await hubProxy.hubMethod1();

// Both parameters and return types are strongly typed.
const value = await hubProxy.hubMethod2("message", 99); // Type inference works.

subscription.dispose();

The example of the actual generated code exists in /samples/console.typescript/generated so please have a look if you are interested.

Packages

• TypedSignalR.Client.TypeScript.Attributes
• TypedSignalR.Client.TypeScript.Analyzer
• TypedSignalR.Client.TypeScript.Generator

Install Using .NET Tool

Use TypedSignalR.Client.TypeScript.Generatorr(CLI Tool) to generate TypeScript source code to provide strongly typed SignalR clients. TypedSignalR.Client.TypeScript.Generatorr can be easily installed using .NET Global Tools. You can use the installed tools with the command dotnet tsts(TypedSignalR.Client.TypeScript).

# install
# TypedSignalR.Client.TypeScript CLI (dotnet tool) requires .NET 7, but your app TFM can use .NET 6, etc.
$ dotnet tool install --global TypedSignalR.Client.TypeScript.Generator
$ dotnet tsrts help

# update
$ dotnet tool update --global TypedSignalR.Client.TypeScript.Generator

Usage

First, add the following packages to your project. TypedSignalR.Client.TypeScript.Analyzer is optional, but recommended.

$ dotnet add package TypedSignalR.Client.TypeScript.Attributes
$ dotnet add package TypedSignalR.Client.TypeScript.Analyzer (optional, but recommended.)
$ dotnet add package Tapper.Analyzer (optional, but recommended.)

By adding TypedSignalR.Client.TypeScript.Attributes package, you can use three attributes.

• HubAttribute
• ReceiverAttribute
• TranspilationSourceAttribute

Then, annotate HubAttribute and ReceiverAttribute to each interface definitions of Hub and Receiver of SignalR. Also, annotate TranspilationSourceAttribute to user-defined types used in the interface definition of Hub and Receiver. Adding this attribute is relatively easy if you add the TypedSignalR.Client.TypeScript.Analyzer to your project.

using Tapper;
using TypedSignalR.Client;

namespace App.Interfaces.Chat;

[Hub] // <- Add Attribute
public interface IChatHub
{
    Task Join(string username);
    Task Leave();
    Task<IEnumerable<string>> GetParticipants();
    Task SendMessage(string message);
}

[Receiver] // <- Add Attribute
public interface IChatReceiver
{
    Task OnReceiveMessage(Message message);
    Task OnLeave(string username, DateTime dateTime);
    Task OnJoin(string username, DateTime dateTime);
}

[TranspilationSource] // <- Add Attribute
public record Message(string Username, string Content, DateTime TimeStamp);

Finally, enter the following command. This command analyzes C# and generates TypeScript code.

$ dotnet tsrts --project path/to/Project.csproj --output generated

The generated code can be used as follows. There are two important APIs that are generated.

• getHubProxyFactory
• getReceiverRegister

import { HubConnectionBuilder } from "@microsoft/signalr";
import { getHubProxyFactory, getReceiverRegister } from "./generated/TypedSignalR.Client";
import { IChatReceiver } from "./generated/TypedSignalR.Client/App.Interfaces.Chat";
import { Message } from "./generated/App.Interfaces.Chat";

const connection = new HubConnectionBuilder()
    .withUrl("https://example.com/hubs/chathub")
    .build();

const receiver: IChatReceiver = {
    onReceiveMessage: (message: Message): Promise<void> => {...},
    onLeave: (username: string, dateTime: string | Date): Promise<void> => {...},
    onJoin: (username: string, dateTime: string | Date): Promise<void> => {...}
}

// The argument of getHubProxyFactory is a string literal type, not a string type.
// Therefore, there is no need to worry about typos.
const hubProxy = getHubProxyFactory("IChatHub")
    .createHubProxy(connection);

// Also, the argument of getReceiverRegister is a string literal type, not a string type.
// Therefore, again, there is no need to worry about typos.
const subscription = getReceiverRegister("IChatReceiver")
    .register(connection, receiver)

await connection.start()

await hubProxy.join(username)

const participants = await hubProxy.getParticipants()

// ...

Supported Types

TypedSignalR.Client.TypeScript uses a library named nenoNaninu/Tapper to convert C# types to TypeScript types. Please read Tapper's README for details on the correspondence between C# types and TypeScript types. Here is a brief introduction of which types are supported.

Built-in Supported Types

bool byte sbyte char decimal double float int uint long ulong short ushort object string Uri Guid DateTime System.Nullable<T> byte[] T[] System.Array ArraySegment<T> List<T> LinkedList<T> Queue<T> Stack<T> HashSet<T> IEnumerable<T> IReadOnlyCollection<T> ICollection<T> IList<T> ISet<T> Dictionary<TKey, TValue> IDictionary<TKey, TValue> IReadOnlyDictionary<TKey, TValue> Tuple

User Defined Types

Of course, you can use user-defined types as well as Built-in Supported Types. To transpile C# user-defined types to TypeScript types, annotate TranspilationSourceAttribute.

using Tapper;

[TranspilationSource] // <- Add attribute!
public class CustomType
{
    public List<int>? List { get; }
    public int Value { get; }
    public Guid Id { get; }
    public DateTime DateTime { get; }
}

[TranspilationSource] // <- Add attribute!
public enum MyEnum
{
    Zero = 0,
    One = 1,
    Two = 1 << 1,
    Four = 1 << 2,
}

[TranspilationSource] // <- Add attribute!
public record CustomType2(float Value, DateTime ReleaseDate);

Analyzer

User-defined types used in parameters and return values of methods defined within interfaces annotated with Hub or Receiver must be annotated with TranspilationSource. The Analyzer checks in real-time whether this rule is followed. If not, the IDE will tell you.

Streaming Support

SignalR supports both server-to-client streaming and client-to-server streaming.

TypedSignalR.Client.TypeScript supports both server-to-client streaming and client-to-server streaming. If you use IAsyncEnumerable<T>, Task<IAsyncEnumerable<T>>, or Task<ChannelReader<T>> for the method return type, it is analyzed as server-to-client streaming. And if IAsyncEnumerable<T> or ChannelReader<T> is used in the method parameter, it is analyzed as client-to-server streaming.

When using server-to-client streaming, a single CancellationToken can be used as a method parameter (Note: CancellationToken cannot be used as a parameter except for server-to-client streaming).

// C# source code
[Hub]
public interface IMyStreamingHub
{
    // Server-to-Client streaming
    // Return type : IAsyncEnumerable<T> or Task<IAsyncEnumerable<T>> or Task<ChannelReader<T>>
    // Parameter : CancellationToken can use.
    Task<ChannelReader<MyStreamItem>> ServerToClientStreaming(MyType instance, int init, CancellationToken cancellationToken);

    // Client-to-Server streaming
    // Return type : Task (not Task<T>)
    // Parameter : IAsyncEnumerable<T> and ChannelReader<T> can use as stream from client to server.
    Task ClientToServerStreaming(MyType instance, ChannelReader<MyStreamItem> stream);
}

// Usage in TypeScript
// Parameters and return types are strongly typed by generated TypeScript code

const connection: HubConnection = ...;

const hubProxy = getHubProxyFactory("IMyStreamingHub")
    .createHubProxy(connection);

await connection.start();

const instance: MyType = ...;

// subscribe server to client streaming message
hubProxy.serverToClientStreaming(instance, 99) // IStreamResult<MyStreamItem>
    .subscribe({
        next: (value: MyStreamItem): void => {
            console.log(value)
        },
        error: (err: any): void => {
            console.log(err)
        },
        complete: (): void => {
            console.log("complete")
        }
    });

const subject = new Subject<MyStreamItem>(); // stream

// set client to server stream
await hubProxy.clientToServerStreaming(instance, subject);

const item: MyStreamItem = ...;
subject.next(item); // write item to stream
subject.next(item);
subject.complete();

Client Results Support

.NET 7 and later, you can use client results.

TypedSignalR.Client.TypeScript supports client results. If you use Task<T> for the method return type in the receiver interface, you can use client results.

// C# source code
[Receiver]
public interface IMyHubReceiver
{
    // Return type: Task<T> 
    Task<Guid> GetGuidFromClient();
}

// Usage in TypeScript
// Parameters and return types are strongly typed by generated TypeScript code

const connection: HubConnection = ...;

const receiver: IMyHubReceiver = {
    getGuidFromClient: (): Promise<string> => {
        // return value.
        return Promise.resolve("ba3088bb-e7ea-4924-b01b-695e879bb166");
    }
}

const subscription = getReceiverRegister("IMyHubReceiver")
    .register(connection, receiver);

MessagePack Hub Protocol Support

This tool can generate TypeScript code to use the MessagePack Hub Protocol. When serializing a user-defined type, use a property name as a key (in other words, it should be serialized as a map, not an array). Therefore, apply [MessagePackObject(true)] to a user-defined type, or use ContractlessStandardResolver. The default configuration for MessagePack Hub Protocol includes the ContractlessStandardResolver.

Default Configuration in ASP.NET Core

Calling AddMessagePackProtocol is required to use the MessagePack Hub Protocol. For more information, please see the official documentation.

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddSignalR()
    .AddJsonProtocol()
    .AddMessagePackProtocol();

If you do not set any options in AddMessagePackProtocol, use the following command.

$ dotnet tsrts --project path/to/Project.csproj --output generated --serializer MessagePack --naming-style none --enum name

Recommended Configuration

SignalR MessagePack Hub Protocol serializes an enum as a string by default. The following configuration is required to serialize an enum as an integer value.

var builder = WebApplication.CreateBuilder(args);

builder.Services.AddSignalR()
    .AddJsonProtocol()
    .AddMessagePackProtocol(options =>
    {
        options.SerializerOptions = MessagePackSerializerOptions.Standard
            .WithResolver(ContractlessStandardResolver.Instance)
            .WithSecurity(MessagePackSecurity.UntrustedData);
    });

If you set up the above configuration, use the following command

$ dotnet tsrts --project path/to/Project.csproj --output generated --serializer MessagePack --naming-style none

Related Work

• nenoNaninu/TypedSignalR.Client
  • C# Source Generator to create strongly typed SignalR clients.
• nenoNaninu/TypedSignalR.Client.DevTools
  • SignalR development tools inspired by SwaggerUI.
• nenoNaninu/Tapper
  • A Tool Transpiling C# Type into TypeScript Type.
• nenoNaninu/AspNetCore.SignalR.OpenTelemetry
  • SignalR instrumentation library for OpenTelemetry.