{"slug":"dotnet-signalr","title":"dotnet-signalr","summary":"Implement or review SignalR hubs, streaming, reconnection, transport, and real-time delivery patterns in ASP.NET Core applications.","platform":"Claude","tags":[],"authorName":"LLM Mart","authorSlug":"llm-mart","score":0,"source":"github","price":null,"verified":false,"createdAt":"2026-09-27T21:00:39.373504Z","repo":{"url":"https://github.com/Postpartum-genushyacinthus29/dotnet-skills","stars":12,"forks":1,"license":"MIT","updatedAt":"2026-09-27T19:34:14Z"},"bodyHtml":"
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name: dotnet-signalr\nversion: \"1.0.0\"\ncategory: \"Web\"\ndescription: \"Implement or review SignalR hubs, streaming, reconnection, transport, and real-time delivery patterns in ASP.NET Core applications.\"\ncompatibility: \"Requires ASP.NET Core SignalR server or client code.\"

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SignalR

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Trigger On

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Documentation

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References

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Workflow

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

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Strongly-Typed Hub (Recommended)

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// Define the client interface\npublic interface IChatClient\n{\n    Task ReceiveMessage(string user, string message);\n    Task UserJoined(string user);\n    Task UserLeft(string user);\n}\n\n// Implement the strongly-typed hub\npublic class ChatHub : Hub<IChatClient>\n{\n    public async Task SendMessage(string user, string message)\n    {\n        // Compiler checks client method calls\n        await Clients.All.ReceiveMessage(user, message);\n    }\n\n    public override async Task OnConnectedAsync()\n    {\n        await Clients.Others.UserJoined(Context.User?.Identity?.Name ?? \"Anonymous\");\n        await base.OnConnectedAsync();\n    }\n\n    public override async Task OnDisconnectedAsync(Exception? exception)\n    {\n        await Clients.Others.UserLeft(Context.User?.Identity?.Name ?? \"Anonymous\");\n        await base.OnDisconnectedAsync(exception);\n    }\n}\n
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Using Groups for Targeted Messaging

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public class NotificationHub : Hub<INotificationClient>\n{\n    public async Task JoinGroup(string groupName)\n    {\n        await Groups.AddToGroupAsync(Context.ConnectionId, groupName);\n        await Clients.Group(groupName).UserJoined(Context.User?.Identity?.Name);\n    }\n\n    public async Task LeaveGroup(string groupName)\n    {\n        await Groups.RemoveFromGroupAsync(Context.ConnectionId, groupName);\n    }\n\n    public async Task SendToGroup(string groupName, string message)\n    {\n        await Clients.Group(groupName).ReceiveNotification(message);\n    }\n}\n
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Hub Method with Custom Object Parameters (API Versioning)

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// Use custom objects to avoid breaking changes\npublic class SendMessageRequest\n{\n    public string Message { get; set; } = string.Empty;\n    public string? Recipient { get; set; }  // Added later without breaking clients\n    public int? Priority { get; set; }       // Added later without breaking clients\n}\n\npublic class ChatHub : Hub<IChatClient>\n{\n    public async Task SendMessage(SendMessageRequest request)\n    {\n        // Handle both old and new clients\n        if (request.Recipient != null)\n        {\n            await Clients.User(request.Recipient).ReceiveMessage(request.Message);\n        }\n        else\n        {\n            await Clients.All.ReceiveMessage(request.Message);\n        }\n    }\n}\n
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Client Patterns

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JavaScript Client with Automatic Reconnection

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const connection = new signalR.HubConnectionBuilder()\n    .withUrl(\"/chatHub\")\n    .withAutomaticReconnect([0, 2000, 5000, 10000, 30000]) // Retry delays\n    .configureLogging(signalR.LogLevel.Information)\n    .build();\n\n// Handle reconnection events\nconnection.onreconnecting(error => {\n    console.log(\"Reconnecting...\", error);\n    updateUIForReconnecting();\n});\n\nconnection.onreconnected(connectionId => {\n    console.log(\"Reconnected with ID:\", connectionId);\n    // Rejoin groups - reconnection does not restore group membership\n    rejoinGroups();\n    updateUIForConnected();\n});\n\nconnection.onclose(error => {\n    console.log(\"Connection closed\", error);\n    updateUIForDisconnected();\n});\n\nasync function start() {\n    try {\n        await connection.start();\n        console.log(\"SignalR Connected\");\n    } catch (err) {\n        console.log(err);\n        setTimeout(start, 5000);\n    }\n}\n\nstart();\n
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.NET Client with Reconnection

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var connection = new HubConnectionBuilder()\n    .WithUrl(\"https://localhost:5001/chatHub\", options =>\n    {\n        options.AccessTokenProvider = () => Task.FromResult(GetAccessToken());\n    })\n    .WithAutomaticReconnect()\n    .Build();\n\nconnection.Reconnecting += error =>\n{\n    _logger.LogWarning(\"Connection lost. Reconnecting: {Error}\", error?.Message);\n    return Task.CompletedTask;\n};\n\nconnection.Reconnected += connectionId =>\n{\n    _logger.LogInformation(\"Reconnected with ID: {ConnectionId}\", connectionId);\n    // Rejoin groups after reconnection\n    return RejoinGroupsAsync();\n};\n\nconnection.Closed += async error =>\n{\n    _logger.LogError(\"Connection closed: {Error}\", error?.Message);\n    await Task.Delay(Random.Shared.Next(0, 5) * 1000);\n    await connection.StartAsync();\n};\n\nawait connection.StartAsync();\n
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Server Configuration

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Hub Registration with Authentication

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var builder = WebApplication.CreateBuilder(args);\n\nbuilder.Services.AddSignalR(options =>\n{\n    options.EnableDetailedErrors = builder.Environment.IsDevelopment();\n    options.MaximumReceiveMessageSize = 64 * 1024; // 64 KB\n    options.StreamBufferCapacity = 10;\n    options.KeepAliveInterval = TimeSpan.FromSeconds(15);\n    options.ClientTimeoutInterval = TimeSpan.FromSeconds(30);\n})\n.AddMessagePackProtocol(); // Binary protocol for performance\n\nbuilder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)\n    .AddJwtBearer(options =>\n    {\n        options.Events = new JwtBearerEvents\n        {\n            OnMessageReceived = context =>\n            {\n                // Read token from query string for WebSocket connections\n                var accessToken = context.Request.Query[\"access_token\"];\n                var path = context.HttpContext.Request.Path;\n                if (!string.IsNullOrEmpty(accessToken) && path.StartsWithSegments(\"/hubs\"))\n                {\n                    context.Token = accessToken;\n                }\n                return Task.CompletedTask;\n            }\n        };\n    });\n\nvar app = builder.Build();\n\napp.UseAuthentication();\napp.UseAuthorization();\n\napp.MapHub<ChatHub>(\"/hubs/chat\");\n
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Sending Messages from Outside a Hub

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public class NotificationService\n{\n    private readonly IHubContext<NotificationHub, INotificationClient> _hubContext;\n\n    public NotificationService(IHubContext<NotificationHub, INotificationClient> hubContext)\n    {\n        _hubContext = hubContext;\n    }\n\n    public async Task NotifyAllAsync(string message)\n    {\n        await _hubContext.Clients.All.ReceiveNotification(message);\n    }\n\n    public async Task NotifyUserAsync(string userId, string message)\n    {\n        await _hubContext.Clients.User(userId).ReceiveNotification(message);\n    }\n\n    public async Task NotifyGroupAsync(string groupName, string message)\n    {\n        await _hubContext.Clients.Group(groupName).ReceiveNotification(message);\n    }\n}\n
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Scaling with Redis Backplane

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builder.Services.AddSignalR()\n    .AddStackExchangeRedis(connectionString, options =>\n    {\n        options.Configuration.ChannelPrefix = RedisChannel.Literal(\"MyApp\");\n    });\n
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Anti-Patterns to Avoid

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Anti-PatternWhy It's BadBetter Approach
Storing state in Hub propertiesHub instances are created per method callUse IMemoryCache, database, or external store
Instantiating Hub directlyBypasses SignalR infrastructureUse IHubContext<THub> for external messaging
Not awaiting SendAsync callsMessages may not be sent before hub method completesAlways await async hub calls
Adding method parameters without versioningBreaking change for existing clientsUse custom object parameters
Ignoring reconnection group lossClients lose group membership on reconnectRe-add to groups in OnConnectedAsync or client reconnect handler
Large payloads over SignalRMemory pressure, bandwidth issuesUse REST/gRPC for bulk data, SignalR for notifications
Missing backplane in multi-serverMessages only reach clients on same serverUse Redis backplane or Azure SignalR Service
Exposing ORM entities directlyMay serialize sensitive dataUse DTOs with explicit properties
Not validating incoming messagesSecurity risk after initial authValidate every hub method input
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Best Practices

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Connection Management

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    \n
  1. Enable automatic reconnection with exponential backoff delays
    2. \n
  2. Handle group rejoining explicitly after reconnection (connection ID changes)
    3. \n
  3. Implement heartbeat monitoring on the client to detect stale connections
    4. \n
  4. Use sticky sessions when scaling across multiple servers (unless using Azure SignalR Service)
    5. \n
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Performance

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    \n
  1. Use MessagePack protocol for smaller message sizes and faster serialization
    2. \n
  2. Throttle high-frequency events like typing indicators or mouse movements
    3. \n
  3. Batch messages when possible instead of many small sends
    4. \n
  4. Set appropriate buffer sizes based on expected message throughput
    5. \n
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Security

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    \n
  1. Authenticate at connection time using JWT tokens via query string
    2. \n
  2. Authorize hub methods using [Authorize] attribute
    3. \n
  3. Validate all incoming messages even after authentication
    4. \n
  4. Use HTTPS for all SignalR connections
    5. \n
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API Design

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    \n
  1. Use strongly-typed hubs to catch client method name typos at compile time
    2. \n
  2. Use custom object parameters to enable backward-compatible API evolution
    3. \n
  3. Version hub names (e.g., ChatHubV2) for breaking changes
    4. \n
  4. Keep hub methods thin and delegate business logic to services
    5. \n
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Observability

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    \n
  1. Log connection events (connect, disconnect, reconnect)
    2. \n
  2. Track transport type used by each connection
    3. \n
  3. Monitor message delivery latency and failure rates
    4. \n
  4. Integrate with Application Insights or other APM tools
    5. \n
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Deliver

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Validate

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