dotnet-signalr

SignalR

Trigger On

• building chat, notification, collaboration, or live-update features
• debugging hub lifetime, connection state, or transport issues
• deciding whether SignalR or another transport better fits the scenario
• implementing real-time broadcasting to groups of connected clients
• scaling SignalR across multiple servers

Documentation

• ASP.NET Core SignalR Overview
• SignalR Hubs
• SignalR API Design Considerations
• SignalR Production Hosting and Scaling
• SignalR Configuration

References

• patterns.md - Detailed hub patterns, streaming, groups, presence, and advanced messaging techniques
• anti-patterns.md - Common SignalR mistakes and how to avoid them

Workflow

1. Use SignalR for broadcast-style or connection-oriented real-time features; do not force gRPC into hub-style fan-out scenarios.
2. Model hub contracts intentionally and keep hub methods thin, delegating durable work elsewhere.
3. Plan for reconnection, backpressure, auth, and fan-out costs instead of treating real-time messaging as stateless request/response.
4. Use groups, presence, and connection metadata deliberately so scale-out behavior is understandable.
5. If Native AOT or trimming is in play, validate supported protocols and serialization choices explicitly.
6. Test connection behavior and failure modes, not just happy-path message delivery.

Hub Patterns

Strongly-Typed Hub (Recommended)

// Define the client interface
public interface IChatClient
{
    Task ReceiveMessage(string user, string message);
    Task UserJoined(string user);
    Task UserLeft(string user);
}

// Implement the strongly-typed hub
public class ChatHub : Hub<IChatClient>
{
    public async Task SendMessage(string user, string message)
    {
        // Compiler checks client method calls
        await Clients.All.ReceiveMessage(user, message);
    }

    public override async Task OnConnectedAsync()
    {
        await Clients.Others.UserJoined(Context.User?.Identity?.Name ?? "Anonymous");
        await base.OnConnectedAsync();
    }

    public override async Task OnDisconnectedAsync(Exception? exception)
    {
        await Clients.Others.UserLeft(Context.User?.Identity?.Name ?? "Anonymous");
        await base.OnDisconnectedAsync(exception);
    }
}