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.NET Aspire Azure Web PubSub integration
This article describes the .NET Aspire Azure Web PubSub integration features and capabilities.
how-to
04/09/2025

.NET Aspire Azure Web PubSub integration

[!INCLUDE includes-hosting-and-client]

Azure Web PubSub is a fully managed real-time messaging service that enables you to build real-time web applications using WebSockets and publish-subscribe patterns. The .NET Aspire Azure Web PubSub integration enables you to connect to Azure Web PubSub instances from your .NET applications.

Hosting integration

The .NET Aspire Azure Web PubSub hosting integration models the Web PubSub resources as the following types:

  • xref:Aspire.Hosting.ApplicationModel.AzureWebPubSubResource: Represents an Azure Web PubSub resource, including connection information to the underlying Azure resource.
  • xref:Aspire.Hosting.ApplicationModel.AzureWebPubSubHubResource: Represents a Web PubSub hub settings resource, which contains the settings for a hub. For example, you can specify if the hub allows anonymous connections or add event handlers to the hub.

To access these types and APIs for expressing them within your app host project, install the 📦 Aspire.Hosting.Azure.WebPubSub NuGet package:

.NET CLI

dotnet add package Aspire.Hosting.Azure.WebPubSub

PackageReference

<PackageReferenceInclude="Aspire.Hosting.Azure.WebPubSub"Version="*" />

For more information, see dotnet add package or Manage package dependencies in .NET applications.

Add an Azure Web PubSub resource

To add an Azure Web PubSub resource to your app host project, call the xref:Aspire.Hosting.AzureWebPubSubExtensions.AddAzureWebPubSub* method providing a name:

varbuilder=DistributedApplication.CreateBuilder(args);varwebPubSub=builder.AddAzureWebPubSub("web-pubsub");builder.AddProject<Projects.ExampleProject>().WithReference(webPubSub);// After adding all resources, run the app...

The preceding code adds an Azure Web PubSub resource named web-pubsub to the app host project. The xref:Aspire.Hosting.ResourceBuilderExtensions.WithReference* method passes the connection information to the ExampleProject project.

Important

When you call AddAzureWebPubSub, it implicitly calls xref:Aspire.Hosting.AzureProvisionerExtensions.AddAzureProvisioning(Aspire.Hosting.IDistributedApplicationBuilder)—which adds support for generating Azure resources dynamically during app startup. The app must configure the appropriate subscription and location. For more information, see Local provisioning: Configuration.

Add an Azure Web PubSub hub resource

When you add an Azure Web PubSub resource, you can also add a child hub resource. The hub resource is a logical grouping of connections and event handlers. To add an Azure Web PubSub hub resource to your app host project, chain a call to the xref:Aspire.Hosting.AzureWebPubSubExtensions.AddHub* method providing a resource and hub name:

varbuilder=DistributedApplication.CreateBuilder(args);varworker=builder.AddProject<Projects.WorkerService>("worker").WithExternalHttpEndpoints();varwebPubSub=builder.AddAzureWebPubSub("web-pubsub");varmessagesHub=webPubSub.AddHub(name:"messages",hubName:"messageHub");// After adding all resources, run the app...

The preceding code adds an Azure Web PubSub hub resource named messages and a hub name of messageHub , which enables the addition of event handlers. To add an event handler, call the xref:Aspire.Hosting.AzureWebPubSubExtensions.AddEventHandler*:

varbuilder=DistributedApplication.CreateBuilder(args);varworker=builder.AddProject<Projects.WorkerService>("worker").WithExternalHttpEndpoints();varwebPubSub=builder.AddAzureWebPubSub("web-pubsub");varmessagesHub=webPubSub.AddHub(name:"messages",hubName:"messageHub");messagesHub.AddEventHandler($"{worker.GetEndpoint("https")}/eventhandler/",systemEvents:["connected"]);// After adding all resources, run the app...

The preceding code adds a worker service project named worker with an external HTTP endpoint. The hub named messages resource is added to the web-pubsub resource, and an event handler is added to the messagesHub resource. The event handler URL is set to the worker service's external HTTP endpoint. For more information, see Azure Web PubSub event handlers.

Provisioning-generated Bicep

When you publish your app, .NET Aspire provisioning APIs generate Bicep alongside the manifest file. Bicep is a domain-specific language for defining Azure resources. For more information, see Bicep Overview.

When you add an Azure Web PubSub resource, the following Bicep is generated:

:::code language="bicep" source="../snippets/azure/AppHost/web-pubsub.module.bicep":::

The preceding Bicep is a module that provisions an Azure Web PubSub resource. Additionally, role assignments are created for the Azure resource in a separate module:

:::code language="bicep" source="../snippets/azure/AppHost/web-pubsub-roles.module.bicep":::

The generated Bicep is a starting point and is influenced by changes to the provisioning infrastructure in C#. Customizations to the Bicep file directly will be overwritten, so make changes through the C# provisioning APIs to ensure they are reflected in the generated files.

Customize provisioning infrastructure

All .NET Aspire Azure resources are subclasses of the xref:Aspire.Hosting.Azure.AzureProvisioningResource type. This type enables the customization of the generated Bicep by providing a fluent API to configure the Azure resources—using the xref:Aspire.Hosting.AzureProvisioningResourceExtensions.ConfigureInfrastructure``1(Aspire.Hosting.ApplicationModel.IResourceBuilder{``0},System.Action{Aspire.Hosting.Azure.AzureResourceInfrastructure}) API. For example, you can configure the kind, consistencyPolicy, locations, and more. The following example demonstrates how to customize the Azure Cosmos DB resource:

:::code language="csharp" source="../snippets/azure/AppHost/Program.ConfigureWebPubSubInfra.cs" id="configure":::

The preceding code:

  • Chains a call to the xref:Aspire.Hosting.AzureProvisioningResourceExtensions.ConfigureInfrastructure* API:
    • The infra parameter is an instance of the xref:Aspire.Hosting.Azure.AzureResourceInfrastructure type.
    • The provisionable resources are retrieved by calling the xref:Azure.Provisioning.Infrastructure.GetProvisionableResources method.
    • The single xref:Azure.Provisioning.WebPubSub.WebPubSubService resource is retrieved.
    • The xref:Azure.Provisioning.WebPubSub.WebPubSubService.Sku?displayProperty=nameWithType object has its name and capacity properties set to Standard_S1 and 5, respectively.
    • A tag is added to the Web PubSub resource with a key of ExampleKey and a value of Example value.

There are many more configuration options available to customize the Web PubSub resource. For more information, see xref:Azure.Provisioning.WebPubSub. For more information, see Azure.Provisioning customization.

Connect to an existing Azure Web PubSub instance

You might have an existing Azure Web PubSub service that you want to connect to. You can chain a call to annotate that your xref:Aspire.Hosting.ApplicationModel.AzureWebPubSubResource is an existing resource:

varbuilder=DistributedApplication.CreateBuilder(args);varexistingPubSubName=builder.AddParameter("existingPubSubName");varexistingPubSubResourceGroup=builder.AddParameter("existingPubSubResourceGroup");varwebPubSub=builder.AddAzureWebPubSub("web-pubsub").AsExisting(existingPubSubName,existingPubSubResourceGroup);builder.AddProject<Projects.ExampleProject>().WithReference(webPubSub);// After adding all resources, run the app...

For more information on treating Azure Web PubSub resources as existing resources, see Use existing Azure resources.

Alternatively, instead of representing an Azure Web PubSub resource, you can add a connection string to the app host. Which is a weakly-typed approach that's based solely on a string value. To add a connection to an existing Azure Web PubSub service, call the xref:Aspire.Hosting.ParameterResourceBuilderExtensions.AddConnectionString%2A method:

varbuilder=DistributedApplication.CreateBuilder(args);varwebPubSub=builder.ExecutionContext.IsPublishMode?builder.AddAzureWebPubSub("web-pubsub"):builder.AddConnectionString("web-pubsub");builder.AddProject<Projects.ExampleProject>().WithReference(webPubSub);// After adding all resources, run the app...

[!INCLUDE connection-strings-alert]

The connection string is configured in the app host's configuration, typically under User Secrets, under the ConnectionStrings section:

{ "ConnectionStrings": { "web-pubsub": "https://{account_name}.webpubsub.azure.com" } }

For more information, see Add existing Azure resources with connection strings.

Client integration

The .NET Aspire Azure Web PubSub client integration is used to connect to an Azure Web PubSub service using the xref:Azure.Messaging.WebPubSub.WebPubSubServiceClient. To get started with the .NET Aspire Azure Web PubSub service client integration, install the 📦 Aspire.Azure.Messaging.WebPubSub NuGet package in the application.

.NET CLI

dotnet add package Aspire.Azure.Messaging.WebPubSub

PackageReference

<PackageReferenceInclude="Aspire.Azure.Messaging.WebPubSub"Version="*" />

Supported Web PubSub client types

The following Web PubSub client types are supported by the library:

Azure client typeAzure options class.NET Aspire settings class
xref:Azure.Messaging.WebPubSub.WebPubSubServiceClientxref:Azure.Messaging.WebPubSub.WebPubSubServiceClientOptionsxref:Aspire.Azure.Messaging.WebPubSub.AzureMessagingWebPubSubSettings

Add Web PubSub client

In the Program.cs file of your client-consuming project, call the xref:Microsoft.Extensions.Hosting.AspireWebPubSubExtensions.AddAzureWebPubSubServiceClient* extension method to register a WebPubSubServiceClient for use via the dependency injection container. The method takes a connection name parameter:

builder.AddAzureWebPubSubServiceClient(connectionName:"web-pubsub");

Tip

The connectionName parameter must match the name used when adding the Web PubSub resource in the app host project. For more information, see Add an Azure Web PubSub resource.

After adding the WebPubSubServiceClient, you can retrieve the client instance using dependency injection. For example, to retrieve your data source object from an example service define it as a constructor parameter and ensure the ExampleService class is registered with the dependency injection container:

publicclassExampleService(WebPubSubServiceClientclient){// Use client...}

For more information, see:

Add keyed Web PubSub client

There might be situations where you want to register multiple WebPubSubServiceClient instances with different connection names. To register keyed Web PubSub clients, call the xref:Microsoft.Extensions.Hosting.AspireWebPubSubExtensions.AddKeyedAzureWebPubSubServiceClient* method:

builder.AddKeyedAzureWebPubSubServiceClient(name:"messages");builder.AddKeyedAzureWebPubSubServiceClient(name:"commands");

Important

When using keyed services, it's expected that your Web PubSub resource configured two named hubs, one for the messages and one for the commands.

Then you can retrieve the client instances using dependency injection. For example, to retrieve the clients from a service:

publicclassExampleService([KeyedService("messages")]WebPubSubServiceClientmessagesClient,[KeyedService("commands")]WebPubSubServiceClientcommandsClient){// Use clients...}

If you want to register a single WebPubSubServiceClient instance with a specific connection name, there's an overload that uses the connection name as the service key. Call the AddKeyedAzureWebPubSubServiceClient method. This method registers the client as a singleton service in the dependency injection container.

builder.AddKeyedAzureWebPubSubServiceClient(connectionName:"web-pubsub");

For more information, see Keyed services in .NET.

Configuration

The .NET Aspire Azure Web PubSub library provides multiple options to configure the Azure Web PubSub connection based on the requirements and conventions of your project. Either an Endpoint or a ConnectionString must be supplied.

Use a connection string

When using a connection string from the ConnectionStrings configuration section, you can provide the name of the connection string when calling AddAzureWebPubSubServiceClient:

builder.AddAzureWebPubSubServiceClient("web-pubsub", settings =>settings.HubName="your_hub_name");

The connection information is retrieved from the ConnectionStrings configuration section. Two connection formats are supported:

  • Service endpoint (recommended): Uses the service endpoint with DefaultAzureCredential.

    { "ConnectionStrings": { "web-pubsub": "https://{account_name}.webpubsub.azure.com" } }

  • Connection string: Includes an access key.

    { "ConnectionStrings": { "web-pubsub": "Endpoint=https://{account_name}.webpubsub.azure.com;AccessKey={account_key}" } }

Use configuration providers

The library supports xref:Microsoft.Extensions.Configuration. It loads settings from configuration using the Aspire:Azure:Messaging:WebPubSub key:

{ "Aspire": { "Azure": { "Messaging": { "WebPubSub": { "DisableHealthChecks": true, "HubName": "your_hub_name" } } } } }

For the complete Azure OpenAI client integration JSON schema, see Aspire.Azure.Messaging.WebPubSub/ConfigurationSchema.json.

Use inline delegates

You can configure settings inline:

builder.AddAzureWebPubSubServiceClient("web-pubsub", settings =>settings.DisableHealthChecks=true);

[!INCLUDE integration-observability-and-telemetry]

Logging

The .NET Aspire Azure Web PubSub integration uses the following log categories:

  • Azure
  • Azure.Core
  • Azure.Identity
  • Azure.Messaging.WebPubSub

Tracing

The .NET Aspire Azure Web PubSub integration will emit the following tracing activities using OpenTelemetry:

  • Azure.Messaging.WebPubSub.*

Metrics

The .NET Aspire Azure Web PubSub integration currently doesn't support metrics by default due to limitations with the Azure SDK for .NET. If that changes in the future, this section will be updated to reflect those changes.

See also

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