Azure Web PubSub extension of isolated-process Azure Functions client library for .NET - version 1.7.0-beta.1

This extension defines the binding types and triggers in the .NET isolated worker process for Azure Functions, allowing you to write functions that respond to any event published to Web PubSub.

Source code | Package | API reference documentation | Product documentation | Samples

Getting started

Install the package

Install the client library from NuGet:

dotnet add package Microsoft.Azure.Functions.Worker.Extensions.WebPubSub --prerelease


You must have an Azure subscription and an Azure resource group with a Web PubSub resource. Follow this step-by-step tutorial to create an Azure Web PubSub instance.

Authenticate the client

In order to let the extension work with Azure Web PubSub service, you will need to provide a valid ConnectionString.

You can find the Keys for you Azure Web PubSub service in the Azure Portal.

The AzureWebJobsStorage connection string is used to preserve the processing checkpoint information as required refer to Storage considerations

For the local development use the local.settings.json file to store the connection string, <connection-string> can be set to WebPubSubConnectionString as default supported in the extension, or you can set customized names by mapping it with Connection = <connection-string> in function binding attributes:

  "Values": {
    "AzureWebJobsStorage": "UseDevelopmentStorage=true",
    "<connection-string>": "Endpoint=https://<webpubsub-name>;AccessKey=<access-key>;Version=1.0;"

When deployed use the application settings to set the connection string.

Key concepts

Using Web PubSub input binding

Please follow the input binding tutorial to learn about using this extension for building WebPubSubConnection to create Websockets connection to service with input binding.

Using Web PubSub output binding

Please follow the output binding tutorial to learn about using this extension for publishing Web PubSub messages.

Using Web PubSub trigger

Please follow the trigger binding tutorial to learn about triggering an Azure Function when an event is sent from service upstream.

In Connect and UserEvent events, function will respect return values to send back service. Then service will depend on the response to proceed the request or else. The responses and events are paired. For example, Connect will only respect ConnectEventResponse or EventErrorResponse, and ignore other returns. When EventErrorResponse is returned, service will drop client connection.


Functions that uses Web PubSub input binding

Use WebPubSubConnectionInput to build the client negotiate URL.

public static HttpResponseData Run([HttpTrigger(AuthorizationLevel.Anonymous)] HttpRequestData req,
[WebPubSubConnectionInput(Hub = "<web_pubsub_hub>", Connection = "<web_pubsub_connection_name>")] WebPubSubConnection connectionInfo)
    var response = req.CreateResponse(HttpStatusCode.OK);
    return response;

Use WebPubSubContextInput to read Web PubSub request under HttpTrigger. This is useful when work with Static Web Apps which supports HttpTrigger functions only.

// validate method when upstream set as http://<func-host>/api/{event}
public static HttpResponseData Validate(
    [HttpTrigger(AuthorizationLevel.Anonymous, "options")] HttpRequestData req,
    [WebPubSubContextInput] WebPubSubContext wpsReq)
    return BuildHttpResponseData(req, wpsReq.Response);

// Respond AbuseProtection to put header correctly.
private static HttpResponseData BuildHttpResponseData(HttpRequestData request, SimpleResponse wpsResponse)
    var response = request.CreateResponse();
    response.StatusCode = (HttpStatusCode)wpsResponse.Status;
    response.Body = response.Body;
    foreach (var header in wpsResponse.Headers)
        response.Headers.Add(header.Key, header.Value);
    return response;

Functions that uses Web PubSub output binding

[WebPubSubOutput(Hub = "<web_pubsub_hub>", Connection = "<web_pubsub_connection_name>")]
public static WebPubSubAction Run([HttpTrigger(AuthorizationLevel.Function, "get", "post")] HttpRequestData req)
    return new SendToAllAction
        Data = BinaryData.FromString($"Hello SendToAll."),
        DataType = WebPubSubDataType.Text

Functions that uses Web PubSub trigger

public static UserEventResponse Run(
[WebPubSubTrigger("<web_pubsub_hub>", WebPubSubEventType.User, "message")] UserEventRequest request)
    return new UserEventResponse("[SYSTEM ACK] Received.");

For more details see the samples README.


Please refer to Monitor Azure Functions for troubleshooting guidance.

Next steps

Read the introduction to Azure Function or creating an Azure Function guide.


See our for details on building, testing, and contributing to this library.

This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.