Add initial support for Resource Templates

[Redth]

This adds some new types and handlers to implement Resource Template functionality according to the spec.

Motivation and Context

Adds more functionality from the spec :)

How Has This Been Tested?

• Unit tests
• Manual testing with mcp-inspector and the Test Server project (List Templates, Read dynamic template resource, and subscribe/unsubscribe validated)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Fixes #20

[PederHP]

This looks correct to me, apart from Annotations which are a draft spec feature and not in the protocol version currently supported and advertised during initialization.

[stephentoub]

Looks good, @Redth, thanks.

Presumably we also want the client-side equivalent, e.g.

csharp-sdk/src/ModelContextProtocol/Client/McpClientExtensions.cs

Lines 142 to 178 in c8c974a

	/// <summary>
	/// Retrieves a sequence of available resources from the server.
	/// </summary>
	/// <param name="client">The client.</param>
	/// <param name="cancellationToken">A token to cancel the operation.</param>
	/// <returns>An asynchronous sequence of resource information.</returns>
	public static async IAsyncEnumerable<Resource> ListResourcesAsync(
	this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
	{
	string? cursor = null;
	do
	{
	var resources = await ListResourcesAsync(client, cursor, cancellationToken).ConfigureAwait(false);
	foreach (var resource in resources.Resources)
	{
	yield return resource;
	}
	cursor = resources.NextCursor;
	}
	while (cursor is not null);
	}
	/// <summary>
	/// Retrieves a list of available resources from the server.
	/// </summary>
	/// <param name="client">The client.</param>
	/// <param name="cursor">A cursor to paginate the results.</param>
	/// <param name="cancellationToken">A token to cancel the operation.</param>
	public static Task<ListResourcesResult> ListResourcesAsync(this IMcpClient client, string? cursor, CancellationToken cancellationToken = default)
	{
	Throw.IfNull(client);
	return client.SendRequestAsync<ListResourcesResult>(
	CreateRequest("resources/list", CreateCursorDictionary(cursor)),
	cancellationToken);
	}

?

[Redth]

Looks good, @Redth, thanks.

Presumably we also want the client-side equivalent, e.g.

csharp-sdk/src/ModelContextProtocol/Client/McpClientExtensions.cs

Lines 142 to 178 in c8c974a

	/// <summary>
	/// Retrieves a sequence of available resources from the server.
	/// </summary>
	/// <param name="client">The client.</param>
	/// <param name="cancellationToken">A token to cancel the operation.</param>
	/// <returns>An asynchronous sequence of resource information.</returns>
	public static async IAsyncEnumerable<Resource> ListResourcesAsync(
	this IMcpClient client, [EnumeratorCancellation] CancellationToken cancellationToken = default)
	{
	string? cursor = null;
	do
	{
	var resources = await ListResourcesAsync(client, cursor, cancellationToken).ConfigureAwait(false);
	foreach (var resource in resources.Resources)
	{
	yield return resource;
	}
	cursor = resources.NextCursor;
	}
	while (cursor is not null);
	}
	/// <summary>
	/// Retrieves a list of available resources from the server.
	/// </summary>
	/// <param name="client">The client.</param>
	/// <param name="cursor">A cursor to paginate the results.</param>
	/// <param name="cancellationToken">A token to cancel the operation.</param>
	public static Task<ListResourcesResult> ListResourcesAsync(this IMcpClient client, string? cursor, CancellationToken cancellationToken = default)
	{
	Throw.IfNull(client);
	return client.SendRequestAsync<ListResourcesResult>(
	CreateRequest("resources/list", CreateCursorDictionary(cursor)),
	cancellationToken);
	}

?

Ok, added client extensions and an integration test.

Stale