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Add SubscribeToResourceAsync overload with handler delegate (#1069)

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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: stephentoub <2642209+stephentoub@users.noreply.github.com>
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Copilot 2025-12-05 18:15:24 -05:00 • committed by GitHub
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146
src/ModelContextProtocol.Core/Client/McpClient.Methods.cs
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@ -561,6 +561,18 @@ public abstract partial class McpClient : McpSession
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>The result of the request.</returns>
/// <exception cref="ArgumentNullException"><paramref name="requestParams"/> is <see langword="null"/>.</exception>
/// <remarks>
/// <para>
/// This method subscribes to resource update notifications but does not register a handler.
/// To receive notifications, you must separately call <see cref="McpSession.RegisterNotificationHandler(string, Func{JsonRpcNotification, CancellationToken, ValueTask})"/>
/// with <see cref="NotificationMethods.ResourceUpdatedNotification"/> and filter for the specific resource URI.
/// To unsubscribe, call <see cref="UnsubscribeFromResourceAsync(UnsubscribeRequestParams, CancellationToken)"/> and dispose the handler registration.
/// </para>
/// <para>
/// For a simpler API that handles both subscription and notification registration in a single call,
/// use <see cref="SubscribeToResourceAsync(Uri, Func{ResourceUpdatedNotificationParams, CancellationToken, ValueTask}, RequestOptions?, CancellationToken)"/>.
/// </para>
/// </remarks>
public Task SubscribeToResourceAsync(
SubscribeRequestParams requestParams,
CancellationToken cancellationToken = default)
@ -575,6 +587,140 @@ public abstract partial class McpClient : McpSession
cancellationToken: cancellationToken).AsTask();
}
/// <summary>
/// Subscribes to a resource on the server and registers a handler for notifications when it changes.
/// </summary>
/// <param name="uri">The URI of the resource to which to subscribe.</param>
/// <param name="handler">The handler to invoke when the resource is updated. It receives <see cref="ResourceUpdatedNotificationParams"/> for the subscribed resource.</param>
/// <param name="options">Optional request options including metadata, serialization settings, and progress tracking.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>
/// A task that completes with an <see cref="IAsyncDisposable"/> that, when disposed, unsubscribes from the resource
/// and removes the notification handler.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="uri"/> or <paramref name="handler"/> is <see langword="null"/>.</exception>
/// <remarks>
/// <para>
/// This method provides a convenient way to subscribe to resource updates and handle notifications in a single call.
/// The returned <see cref="IAsyncDisposable"/> manages both the subscription and the notification handler registration.
/// When disposed, it automatically unsubscribes from the resource and removes the handler.
/// </para>
/// <para>
/// The handler will only be invoked for notifications related to the specified resource URI.
/// Notifications for other resources are filtered out automatically.
/// </para>
/// </remarks>
public Task<IAsyncDisposable> SubscribeToResourceAsync(
Uri uri,
Func<ResourceUpdatedNotificationParams, CancellationToken, ValueTask> handler,
RequestOptions? options = null,
CancellationToken cancellationToken = default)
{
Throw.IfNull(uri);
return SubscribeToResourceAsync(uri.AbsoluteUri, handler, options, cancellationToken);
}
/// <summary>
/// Subscribes to a resource on the server and registers a handler for notifications when it changes.
/// </summary>
/// <param name="uri">The URI of the resource to which to subscribe.</param>
/// <param name="handler">The handler to invoke when the resource is updated. It receives <see cref="ResourceUpdatedNotificationParams"/> for the subscribed resource.</param>
/// <param name="options">Optional request options including metadata, serialization settings, and progress tracking.</param>
/// <param name="cancellationToken">The <see cref="CancellationToken"/> to monitor for cancellation requests. The default is <see cref="CancellationToken.None"/>.</param>
/// <returns>
/// A task that completes with an <see cref="IAsyncDisposable"/> that, when disposed, unsubscribes from the resource
/// and removes the notification handler.
/// </returns>
/// <exception cref="ArgumentNullException"><paramref name="uri"/> or <paramref name="handler"/> is <see langword="null"/>.</exception>
/// <exception cref="ArgumentException"><paramref name="uri"/> is empty or composed entirely of whitespace.</exception>
/// <remarks>
/// <para>
/// This method provides a convenient way to subscribe to resource updates and handle notifications in a single call.
/// The returned <see cref="IAsyncDisposable"/> manages both the subscription and the notification handler registration.
/// When disposed, it automatically unsubscribes from the resource and removes the handler.
/// </para>
/// <para>
/// The handler will only be invoked for notifications related to the specified resource URI.
/// Notifications for other resources are filtered out automatically.
/// </para>
/// </remarks>
public async Task<IAsyncDisposable> SubscribeToResourceAsync(
string uri,
Func<ResourceUpdatedNotificationParams, CancellationToken, ValueTask> handler,
RequestOptions? options = null,
CancellationToken cancellationToken = default)
{
Throw.IfNullOrWhiteSpace(uri);
Throw.IfNull(handler);
// Register a notification handler that filters for this specific resource
IAsyncDisposable handlerRegistration = RegisterNotificationHandler(
NotificationMethods.ResourceUpdatedNotification,
async (notification, ct) =>
{
if (JsonSerializer.Deserialize(notification.Params, McpJsonUtilities.JsonContext.Default.ResourceUpdatedNotificationParams) is { } resourceUpdate &&
UriTemplate.UriTemplateComparer.Instance.Equals(resourceUpdate.Uri, uri))
{
await handler(resourceUpdate, ct).ConfigureAwait(false);
}
});
try
{
// Subscribe to the resource
await SubscribeToResourceAsync(uri, options, cancellationToken).ConfigureAwait(false);
}
catch
{
// If subscription fails, unregister the handler before propagating the exception
await handlerRegistration.DisposeAsync().ConfigureAwait(false);
throw;
}
// Return a disposable that unsubscribes and removes the handler
return new ResourceSubscription(this, uri, handlerRegistration, options);
}
/// <summary>
/// Manages a resource subscription, handling both unsubscription and handler disposal.
/// </summary>
private sealed class ResourceSubscription : IAsyncDisposable
{
private readonly McpClient _client;
private readonly string _uri;
private readonly IAsyncDisposable _handlerRegistration;
private readonly RequestOptions? _options;
private int _disposed;
public ResourceSubscription(McpClient client, string uri, IAsyncDisposable handlerRegistration, RequestOptions? options)
{
_client = client;
_uri = uri;
_handlerRegistration = handlerRegistration;
_options = options;
}
public async ValueTask DisposeAsync()
{
if (Interlocked.Exchange(ref _disposed, 1) != 0)
{
return;
}
try
{
// Unsubscribe from the resource
await _client.UnsubscribeFromResourceAsync(_uri, _options, CancellationToken.None).ConfigureAwait(false);
}
finally
{
// Dispose the notification handler registration
await _handlerRegistration.DisposeAsync().ConfigureAwait(false);
}
}
}
/// <summary>
/// Unsubscribes from a resource on the server to stop receiving notifications about its changes.
/// </summary>