The C# .NET SDK currently only supports legacy versions of Nitric prior to v1. This version is maintained for compatibility with existing projects and not recommended for new projects. New projects should be started using a supported SDK (presented automatically using the `nitric new` command) orget in touch to request an update to the latest version.

.NET - Websocket.On()

Register a handler for connections, disconnections, or messages for the websocket.

using Nitric.Sdk;
using Nitric.Sdk.Function;

var websocket = Nitric.Websocket("public");

websocket.On(WebsocketEventType.Connected, ctx => {
  // handle connections
  return ctx;
});

websocket.On(WebsocketEventType.Disconnected, ctx => {
  // handle disconnections
  return ctx;
});

websocket.On(WebsocketEventType.Message, ctx => {
  // handle message
  return ctx;
});

Nitric.Run();

Parameters

  • Name
    eventType
    Required
    Required
    Type
    WebsocketEventType
    Description

    The type of websocket event to listen for. Can be Connected, Disconnected, or Message.

  • Name
    middleware
    Required
    Required
    Type
    WebsocketMiddleware
    Description

    The middleware function to use as the handler for Websocket events.

Examples

Register a handler for message events

Messages can be read as literal strings using ctx.Req.Message().

websocket.On(WebsocketEventType.Message, ctx => {
    var message = ctx.Req.Message();

    Console.WriteLine($"New Message from {ctx.Req.ConnectionId}: {message}");

    return ctx;
});

Or they can be serialized to a class type using ctx.Req.Message<ClassName>().

class EventUpdate
{
    public float Status { get; set; }
    public string Content { get; set; }
}

websocket.On(WebsocketEventType.Message, ctx => {
    var message = ctx.Req.Message<EventUpdate>();

    Console.WriteLine($"Status: {message.Status}, Message: {message.Content}")

    return ctx;
});

Manage Websocket connections

To store Websocket connections you can use a Nitric collection.

using System;
using Nitric.Sdk.Function;
using Nitric.Sdk.Resource;

class OpenConnection
{
    public string Id { get; set; }
    public Dictionary<string, string> Metadata { get; set; }
}

var websocket = Nitric.Websocket("public");

var collections = Nitric.Collection<OpenConnection>("connections").With(
    CollectionPermission.Writing, CollectionPermission.Deleting
);

websocket.On(WebsocketEventType.Connected, ctx =>
{
    collections.Doc(ctx.Req.ConnectionId).Set(new OpenConnection
    {
        Id = ctx.Req.ConnectionId,
        Metadata = new Dictionary<string, string> { } // store any metadata related to the connection here
    });
    return ctx;
});

websocket.On(WebsocketEventType.Disconnected, ctx =>
{
    collections.Doc(ctx.Req.ConnectionId).Delete();
    return ctx;
});

Nitric.Run();

Chain functions as a single method handler

using System;
using Nitric.Sdk.Function;

class Application
{
    static WebsocketContext ValidateRequest(WebsocketContext ctx, Func<WebsocketContext, WebsocketContext> next)
    {
        // Validate Request
        return next(ctx);
    }

    static WebsocketContext HandleRequest(WebsocketContext ctx, Func<WebsocketContext, WebsocketContext> next)
    {
        // Handle Request
        return next(ctx);
    }

    public static void Main(string[] args) {
        var websocket = Nitric.Websocket("public");

        websocket.On(WebsocketNotificationType.Message, ValidateRequest, HandleRequest);

        Nitric.Run();
    }
}