SignalR Service trigger binding for Azure Functions

The following sample shows a C# function that receives a message event from clients and logs the message content.

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the MIT License. See License.txt in the project root for license information.


using Microsoft.Azure.Functions.Worker;
using Microsoft.Extensions.Logging;

namespace Extensions.SignalR
{
    public static class SignalRTriggerFunctions
    {
        // <snippet_on_connected>
        [Function(nameof(OnConnected))]
        public static void OnConnected(
            [SignalRTrigger("chat", "connections", "connected", ConnectionStringSetting = "SignalRConnection")]
                SignalRInvocationContext invocationContext, FunctionContext functionContext)
        {
            var logger = functionContext.GetLogger(nameof(OnConnected));
            logger.LogInformation("Connection {connectionId} is connected", invocationContext.ConnectionId);
        }
        // </snippet_on_connected>

        // <snippet_on_disconnected>
        [Function(nameof(OnDisconnected))]
        public static void OnDisconnected(
            [SignalRTrigger("chat", "connections", "disconnected", ConnectionStringSetting = "SignalRConnection")]
                SignalRInvocationContext invocationContext, FunctionContext functionContext)
        {
            var logger = functionContext.GetLogger(nameof(OnDisconnected));
            logger.LogInformation("Connection {connectionId} is disconnected. Error: {error}", invocationContext.ConnectionId, invocationContext.Error);
        }
        // </snippet_on_disconnected>

        // <snippet_on_message>
        [Function(nameof(OnClientMessage))]
        public static void OnClientMessage(
            [SignalRTrigger("Hub", "messages", "sendMessage", "content", ConnectionStringSetting = "SignalRConnection")]
                SignalRInvocationContext invocationContext, string content, FunctionContext functionContext)
        {
            var logger = functionContext.GetLogger(nameof(OnClientMessage));
            logger.LogInformation("Connection {connectionId} sent a message. Message content: {content}", invocationContext.ConnectionId, content);
        }
        // </snippet_on_message>
    }
}

SignalR Service trigger binding for C# in-process model has two programming models. Class based model and traditional model. Class based model provides a consistent SignalR server-side programming experience. Traditional model provides more flexibility and is similar to other function bindings.

With class-based model

See Class based model for details.

public class HubName1 : ServerlessHub
{
    [FunctionName("SignalRTest")]
    public Task SendMessage([SignalRTrigger]InvocationContext invocationContext, string message, ILogger logger)
    {
        logger.LogInformation($"Receive {message} from {invocationContext.ConnectionId}.");
    }
}

With a traditional model

Traditional model obeys the convention of Azure Function developed by C#. If you're not familiar with it, you can learn from documents.

[FunctionName("SignalRTest")]
public static Task Run([SignalRTrigger("SignalRTest", "messages", "SendMessage", parameterNames: new string[] {"message"})]InvocationContext invocationContext, string message, ILogger logger)
{
    logger.LogInformation($"Receive {message} from {invocationContext.ConnectionId}.");
}

Because it can be hard to use ParameterNames in the trigger, the following example shows you how to use the SignalRParameter attribute to define the message attribute.

[FunctionName("SignalRTest")]
public static Task Run([SignalRTrigger("SignalRTest", "messages", "SendMessage")]InvocationContext invocationContext, [SignalRParameter]string message, ILogger logger)
{
    logger.LogInformation($"Receive {message} from {invocationContext.ConnectionId}.");
}

app.generic("function1",
    {
        trigger: { "type": "signalRTrigger", "name": "invocation", "direction": "in", "hubName": "hubName1", "event": "SendMessage", "category": "messages" },
        handler: (triggerInput, context) => {
            context.log(`Receive ${context.Arguments[0]} from ${triggerInput.ConnectionId}.`)
        }
    })

Here's binding data in the function.json file:

{
    "type": "signalRTrigger",
    "name": "invocation",
    "hubName": "hubName1",
    "category": "messages",
    "event": "SendMessage",
    "parameterNames": [
        "message"
    ],
    "direction": "in"
}

Here's the JavaScript code:

module.exports = function (context, invocation) {
    context.log(`Receive ${context.bindingData.message} from ${invocation.ConnectionId}.`)
};

The following table explains the properties of the SignalRTrigger attribute.

The following table explains the properties of the SignalRTrigger attribute.