Extension methods on IDistributedApplicationBuilder for subscribing to application level events.

playground/DotnetTool/DotnetTool.AppHost/AppHost.cs

@@ -85,7 +85,7 @@
 
 // Some issues only show up when installing for first time, rather than using existing downloaded versions
 // Use a specific NUGET_PACKAGES path for these playground tools, so we can easily reset them
-builder.Eventing.Subscribe<BeforeStartEvent>(async (evt, _) =>
+builder.OnBeforeStart(async (evt, _) =>
 {
     var nugetPackagesPath = Path.Join(evt.Services.GetRequiredService<IAspireStore>().BasePath, "nuget");
 

src/Aspire.Hosting.Azure.ContainerRegistry/AzureContainerRegistryExtensions.cs

@@ -81,7 +81,7 @@ public static IResourceBuilder<AzureContainerRegistryResource> AddAzureContainer
     /// </summary>
     private static void SubscribeToAddRegistryTargetAnnotations(IDistributedApplicationBuilder builder, AzureContainerRegistryResource registry)
     {
-        builder.Eventing.Subscribe<BeforeStartEvent>((beforeStartEvent, cancellationToken) =>
+        builder.OnBeforeStart((beforeStartEvent, cancellationToken) =>
         {
             foreach (var resource in beforeStartEvent.Model.Resources)
             {

src/Aspire.Hosting.Azure.CosmosDB/AzureCosmosDBExtensions.cs

@@ -485,7 +485,7 @@ public static IResourceBuilder<AzureCosmosDBResource> WithAccessKeyAuthenticatio
         // need to do this later in case builder becomes an emulator after this method is called.
         if (builder.ApplicationBuilder.ExecutionContext.IsRunMode)
         {
-            builder.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((data, _) =>
+            builder.ApplicationBuilder.OnBeforeStart((data, _) =>
             {
                 if (builder.Resource.IsEmulator)
                 {

src/Aspire.Hosting.Azure.Functions/AzureFunctionsProjectResourceExtensions.cs

@@ -154,7 +154,7 @@ private static IResourceBuilder<AzureFunctionsProjectResource> AddAzureFunctions
                 .Resource;
         }
 
-        builder.Eventing.Subscribe<BeforeStartEvent>((data, token) =>
+        builder.OnBeforeStart((data, token) =>
         {
             var removeStorage = true;
             // Look at all of the resources and if none of them use the default storage, then we can remove it.

src/Aspire.Hosting.Azure.PostgreSQL/AzurePostgresExtensions.cs

@@ -306,7 +306,7 @@ public static IResourceBuilder<AzurePostgresFlexibleServerResource> WithPassword
         // need to do this later in case builder becomes an emulator after this method is called.
         if (builder.ApplicationBuilder.ExecutionContext.IsRunMode)
         {
-            builder.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((data, token) =>
+            builder.ApplicationBuilder.OnBeforeStart((data, token) =>
             {
                 if (builder.Resource.IsContainer())
                 {

src/Aspire.Hosting.Azure.Redis/AzureManagedRedisExtensions.cs

@@ -138,7 +138,7 @@ public static IResourceBuilder<AzureManagedRedisResource> WithAccessKeyAuthentic
         // need to do this later in case builder becomes an emulator after this method is called.
         if (builder.ApplicationBuilder.ExecutionContext.IsRunMode)
         {
-            builder.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((data, token) =>
+            builder.ApplicationBuilder.OnBeforeStart((data, token) =>
             {
                 if (builder.Resource.IsContainer())
                 {

src/Aspire.Hosting.Azure.Redis/AzureRedisExtensions.cs

@@ -206,7 +206,7 @@ public static IResourceBuilder<AzureRedisCacheResource> WithAccessKeyAuthenticat
         // need to do this later in case builder becomes an emulator after this method is called.
         if (builder.ApplicationBuilder.ExecutionContext.IsRunMode)
         {
-            builder.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((data, token) =>
+            builder.ApplicationBuilder.OnBeforeStart((data, token) =>
             {
                 if (builder.Resource.IsContainer())
                 {

src/Aspire.Hosting.JavaScript/JavaScriptHostingExtensions.cs

@@ -266,7 +266,7 @@ public static IResourceBuilder<NodeAppResource> AddNodeApp(this IDistributedAppl
 
         if (builder.ExecutionContext.IsRunMode)
         {
-            builder.Eventing.Subscribe<BeforeStartEvent>((_, _) =>
+            builder.OnBeforeStart((_, _) =>
             {
                 // set the command to the package manager executable if the JavaScriptRunScriptAnnotation is present
                 if (resourceBuilder.Resource.TryGetLastAnnotation<JavaScriptRunScriptAnnotation>(out _) &&
@@ -471,7 +471,7 @@ private static IResourceBuilder<TResource> CreateDefaultJavaScriptAppBuilder<TRe
         // ensure the package manager command is set before starting the resource
         if (builder.ExecutionContext.IsRunMode)
         {
-            builder.Eventing.Subscribe<BeforeStartEvent>((_, _) =>
+            builder.OnBeforeStart((_, _) =>
             {
                 if (resourceBuilder.Resource.TryGetLastAnnotation<JavaScriptPackageManagerAnnotation>(out var packageManager))
                 {
@@ -1139,7 +1139,7 @@ private static void AddInstaller<TResource>(IResourceBuilder<TResource> resource
                 .ExcludeFromManifest()
                 .WithCertificateTrustScope(CertificateTrustScope.None);
 
-            resource.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((_, _) =>
+            resource.ApplicationBuilder.OnBeforeStart((_, _) =>
             {
                 // set the installer's working directory to match the resource's working directory
                 // and set the install command and args based on the resource's annotations

src/Aspire.Hosting.Maui/MauiOtlpExtensions.cs

@@ -116,7 +116,7 @@ private static OtlpDevTunnelConfigurationAnnotation CreateOtlpDevTunnelInfrastru
 
         // Manually allocate the stub endpoint so dev tunnel can start
         // Dev tunnels wait for ResourceEndpointsAllocatedEvent before starting
-        appBuilder.Eventing.Subscribe<BeforeStartEvent>((evt, ct) =>
+        appBuilder.OnBeforeStart((evt, ct) =>
         {
             var endpoint = stubResource.Annotations.OfType<EndpointAnnotation>().FirstOrDefault();
             if (endpoint is not null && endpoint.AllocatedEndpoint is null)

src/Aspire.Hosting.Python/PythonAppResourceBuilderExtensions.cs

@@ -491,7 +491,7 @@ private static IResourceBuilder<T> AddPythonAppCore<T>(
             // and the dependencies will be established based on which resources actually exist
             // Only do this in run mode since the installer and venv creator only run in run mode
             var resourceToSetup = resourceBuilder.Resource;
-            builder.Eventing.Subscribe<BeforeStartEvent>((evt, ct) =>
+            builder.OnBeforeStart((evt, ct) =>
             {
                 // Wire up wait dependencies for this resource based on which child resources exist
                 SetupDependencies(builder, resourceToSetup);
@@ -1332,7 +1332,7 @@ private static void AddInstaller<T>(IResourceBuilder<T> builder, bool install) w
                 installerBuilder.WithExplicitStart();
             }
 
-            builder.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((_, _) =>
+            builder.ApplicationBuilder.OnBeforeStart((_, _) =>
             {
                 // Set the installer's working directory to match the resource's working directory
                 // and set the install command and args based on the resource's annotations

src/Aspire.Hosting/ContainerRegistryResourceBuilderExtensions.cs

@@ -120,7 +120,7 @@ public static IResourceBuilder<ContainerRegistryResource> AddContainerRegistry(
     /// </summary>
     private static void SubscribeToAddRegistryTargetAnnotations(IDistributedApplicationBuilder builder, ContainerRegistryResource registry)
     {
-        builder.Eventing.Subscribe<BeforeStartEvent>((beforeStartEvent, cancellationToken) =>
+        builder.OnBeforeStart((beforeStartEvent, cancellationToken) =>
         {
             foreach (var resource in beforeStartEvent.Model.Resources)
             {

src/Aspire.Hosting/DistributedApplicationEventingExtensions.cs

@@ -3,14 +3,51 @@
 
 using Aspire.Hosting.ApplicationModel;
 using Aspire.Hosting.Eventing;
+using Aspire.Hosting.Publishing;
 
 namespace Aspire.Hosting;
 
 /// <summary>
-/// Provides extension methods for subscribing to <see cref="IDistributedApplicationResourceEvent"/> events on resources.
+/// Provides extension methods for subscribing to <see cref="IDistributedApplicationEvent"/> and <see cref="IDistributedApplicationResourceEvent"/> events.
 /// </summary>
 public static class DistributedApplicationEventingExtensions
 {
+    /// <summary>
+    /// Subscribes a callback to the <see cref="BeforeStartEvent"/> event within the AppHost.
+    /// </summary>
+    /// <param name="builder">The distributed application builder.</param>
+    /// <param name="callback">A callback to handle the event.</param>
+    /// <returns>The <paramref name="builder"/> for chaining.</returns>
+    /// <remarks>If you need to ensure you only subscribe to the event once, see <see cref="Lifecycle.IDistributedApplicationEventingSubscriber"/>.</remarks>
+    [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
+    public static T OnBeforeStart<T>(this T builder, Func<BeforeStartEvent, CancellationToken, Task> callback)
+        where T : IDistributedApplicationBuilder
+        => builder.OnApplicationEvent(callback);
+
+    /// <summary>
+    /// Subscribes a callback to the <see cref="BeforePublishEvent"/> event within the AppHost.
+    /// </summary>
+    /// <param name="builder">The distributed application builder.</param>
+    /// <param name="callback">A callback to handle the event.</param>
+    /// <returns>The <paramref name="builder"/> for chaining.</returns>
+    /// <remarks>If you need to ensure you only subscribe to the event once, see <see cref="Lifecycle.IDistributedApplicationEventingSubscriber"/>.</remarks>
+    [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
+    public static T OnBeforePublish<T>(this T builder, Func<BeforePublishEvent, CancellationToken, Task> callback)
+        where T : IDistributedApplicationBuilder
+        => builder.OnApplicationEvent(callback);
+
+    /// <summary>
+    /// Subscribes a callback to the <see cref="AfterPublishEvent"/> event within the AppHost.
+    /// </summary>
+    /// <param name="builder">The distributed application builder.</param>
+    /// <param name="callback">A callback to handle the event.</param>
+    /// <returns>The <paramref name="builder"/> for chaining.</returns>
+    /// <remarks>If you need to ensure you only subscribe to the event once, see <see cref="Lifecycle.IDistributedApplicationEventingSubscriber"/>.</remarks>
+    [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
+    public static T OnAfterPublish<T>(this T builder, Func<AfterPublishEvent, CancellationToken, Task> callback)
+        where T : IDistributedApplicationBuilder
+        => builder.OnApplicationEvent(callback);
+
     /// <summary>
     /// Subscribes a callback to the <see cref="BeforeResourceStartedEvent"/> event within the AppHost.
     /// </summary>
@@ -22,10 +59,10 @@ public static class DistributedApplicationEventingExtensions
     [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
     public static IResourceBuilder<T> OnBeforeResourceStarted<T>(this IResourceBuilder<T> builder, Func<T, BeforeResourceStartedEvent, CancellationToken, Task> callback)
         where T : IResource
-        => builder.OnEvent(callback);
+        => builder.OnResourceEvent(callback);
 
     /// <summary>
-    /// Subscribes a callback to the <see cref="ResourceStoppedEvent"/> event within the AppHost.
+    /// Subscribes a callback to the <see cref="ResourceStoppedEvent"/> event for <paramref name="builder"/>.
     /// </summary>
     /// <typeparam name="T">The resource type.</typeparam>
     /// <param name="builder">The resource builder.</param>
@@ -35,10 +72,10 @@ public static IResourceBuilder<T> OnBeforeResourceStarted<T>(this IResourceBuild
     [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
     public static IResourceBuilder<T> OnResourceStopped<T>(this IResourceBuilder<T> builder, Func<T, ResourceStoppedEvent, CancellationToken, Task> callback)
         where T : IResource
-        => builder.OnEvent(callback);
+        => builder.OnResourceEvent(callback);
 
     /// <summary>
-    /// Subscribes a callback to the <see cref="ConnectionStringAvailableEvent"/> event within the AppHost.
+    /// Subscribes a callback to the <see cref="ConnectionStringAvailableEvent"/> event for <paramref name="builder"/>.
     /// </summary>
     /// <typeparam name="T">The resource type.</typeparam>
     /// <param name="builder">The resource builder.</param>
@@ -48,10 +85,10 @@ public static IResourceBuilder<T> OnResourceStopped<T>(this IResourceBuilder<T>
     [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
     public static IResourceBuilder<T> OnConnectionStringAvailable<T>(this IResourceBuilder<T> builder, Func<T, ConnectionStringAvailableEvent, CancellationToken, Task> callback)
         where T : IResourceWithConnectionString
-        => builder.OnEvent(callback);
+        => builder.OnResourceEvent(callback);
 
     /// <summary>
-    /// Subscribes a callback to the <see cref="InitializeResourceEvent"/> event within the AppHost.
+    /// Subscribes a callback to the <see cref="InitializeResourceEvent"/> event for <paramref name="builder"/>.
     /// </summary>
     /// <typeparam name="T">The resource type.</typeparam>
     /// <param name="builder">The resource builder.</param>
@@ -61,10 +98,10 @@ public static IResourceBuilder<T> OnConnectionStringAvailable<T>(this IResourceB
     [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
     public static IResourceBuilder<T> OnInitializeResource<T>(this IResourceBuilder<T> builder, Func<T, InitializeResourceEvent, CancellationToken, Task> callback)
         where T : IResource
-        => builder.OnEvent(callback);
+        => builder.OnResourceEvent(callback);
 
     /// <summary>
-    /// Subscribes a callback to the <see cref="ResourceEndpointsAllocatedEvent"/> event within the AppHost.
+    /// Subscribes a callback to the <see cref="ResourceEndpointsAllocatedEvent"/> event for <paramref name="builder"/>.
     /// </summary>
     /// <typeparam name="T">The resource type.</typeparam>
     /// <param name="builder">The resource builder.</param>
@@ -74,10 +111,10 @@ public static IResourceBuilder<T> OnInitializeResource<T>(this IResourceBuilder<
     [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
     public static IResourceBuilder<T> OnResourceEndpointsAllocated<T>(this IResourceBuilder<T> builder, Func<T, ResourceEndpointsAllocatedEvent, CancellationToken, Task> callback)
         where T : IResourceWithEndpoints
-        => builder.OnEvent(callback);
+        => builder.OnResourceEvent(callback);
 
     /// <summary>
-    /// Subscribes a callback to the <see cref="ResourceReadyEvent"/> event within the AppHost.
+    /// Subscribes a callback to the <see cref="ResourceReadyEvent"/> event for <paramref name="builder"/>.
     /// </summary>
     /// <typeparam name="T">The resource type.</typeparam>
     /// <param name="builder">The resource builder.</param>
@@ -87,9 +124,17 @@ public static IResourceBuilder<T> OnResourceEndpointsAllocated<T>(this IResource
     [AspireExportIgnore(Reason = "Complex generic delegates with event/CancellationToken types — not ATS-compatible.")]
     public static IResourceBuilder<T> OnResourceReady<T>(this IResourceBuilder<T> builder, Func<T, ResourceReadyEvent, CancellationToken, Task> callback)
         where T : IResource
-        => builder.OnEvent(callback);
+        => builder.OnResourceEvent(callback);
+
+    private static T OnApplicationEvent<T, TEvent>(this T builder, Func<TEvent, CancellationToken, Task> callback)
+        where T : IDistributedApplicationBuilder
+        where TEvent : IDistributedApplicationEvent
+    {
+        builder.Eventing.Subscribe(callback);
+        return builder;
+    }
 
-    private static IResourceBuilder<TResource> OnEvent<TResource, TEvent>(this IResourceBuilder<TResource> builder, Func<TResource, TEvent, CancellationToken, Task> callback)
+    private static IResourceBuilder<TResource> OnResourceEvent<TResource, TEvent>(this IResourceBuilder<TResource> builder, Func<TResource, TEvent, CancellationToken, Task> callback)
         where TResource : IResource
         where TEvent : IDistributedApplicationResourceEvent
     {

src/Aspire.Hosting/ResourceBuilderExtensions.cs

@@ -2892,7 +2892,7 @@ public static IResourceBuilder<TResource> SubscribeHttpsEndpointsUpdate<TResourc
         ArgumentNullException.ThrowIfNull(callback);
 
         var resource = builder.Resource;
-        builder.ApplicationBuilder.Eventing.Subscribe<BeforeStartEvent>((@event, cancellationToken) =>
+        builder.ApplicationBuilder.OnBeforeStart((@event, cancellationToken) =>
         {
             var developerCertificateService = @event.Services.GetRequiredService<IDeveloperCertificateService>();