How to implement a resource provider with v0.3.0-preview.3?

[Kaexburli]

Hello,

I am migrating a project from ModelContextProtocol version 0.2.0-preview.3 to
0.3.0-preview.3 and I'm facing issues with my custom resource provider implementation.

In the previous version, I had a class that implemented IResourceProvider and used a
Resource type, both from the ModelContextProtocol.Server namespace.

My code looked like this:

DocumentationResourceProvider.cs

1 using ModelContextProtocol.Server;
2 using System.Collections.Generic;
3 using System.IO;
4 using System.Threading.Tasks;
5
6 namespace MCPServer
7 {
8     public class DocumentationResourceProvider : IResourceProvider
9     {

10 public async Task<IEnumerable> GetResourcesAsync()
11 {
12 // ... implementation to read .md files and return them
13 }
14 }
15 }

Program.cs (Old Syntax)

1 services.AddMcpServer(mcp =>
2 {
3 mcp.AddResourceProvider();
4 });

After updating the package to 0.3.0-preview.3, the build fails because the
IResourceProvider and Resource types can no longer be found. I noticed the server
configuration syntax has changed to a fluent API, and I've updated my code accordingly:

Program.cs (New Syntax)

1 services.AddMcpServer()
2 .WithResourceProvider()
3 .WithStdioServerTransport();

However, the issue remains because the types themselves seem to have been moved or
removed.

My question is: What is the new way to implement and register a custom resource provider
in version 0.3.0-preview.3? Have the IResourceProvider and Resource types been renamed or
replaced by a new mechanism?

Thanks for your help.

[PederHP]

I don't see any WithResourceProvider() in the current version? I also cannot find anything in 0.2.0-preview.3 - but maybe I'm just bad at searching.

If you want to provide a collection of resources from a type you can do something like this:

csharp-sdk/samples/EverythingServer/ResourceGenerator.cs

Lines 1 to 34 in 15f8e89

	using ModelContextProtocol.Protocol;
	namespace EverythingServer;
	static class ResourceGenerator
	{
	private static readonly List<Resource> _resources = Enumerable.Range(1, 100).Select(i =>
	{
	var uri = $"test://template/resource/{i}";
	if (i % 2 != 0)
	{
	return new Resource
	{
	Uri = uri,
	Name = $"Resource {i}",
	MimeType = "text/plain",
	Description = $"Resource {i}: This is a plaintext resource"
	};
	}
	else
	{
	var buffer = System.Text.Encoding.UTF8.GetBytes($"Resource {i}: This is a base64 blob");
	return new Resource
	{
	Uri = uri,
	Name = $"Resource {i}",
	MimeType = "application/octet-stream",
	Description = Convert.ToBase64String(buffer)
	};
	}
	}).ToList();
	public static IReadOnlyList<Resource> Resources => _resources;
	}

And

csharp-sdk/samples/EverythingServer/Resources/SimpleResourceType.cs

Lines 1 to 39 in 15f8e89

	using ModelContextProtocol.Protocol;
	using ModelContextProtocol.Server;
	using System.ComponentModel;
	namespace EverythingServer.Resources;
	[McpServerResourceType]
	public class SimpleResourceType
	{
	[McpServerResource(UriTemplate = "test://direct/text/resource", Name = "Direct Text Resource", MimeType = "text/plain")]
	[Description("A direct text resource")]
	public static string DirectTextResource() => "This is a direct resource";
	[McpServerResource(UriTemplate = "test://template/resource/{id}", Name = "Template Resource")]
	[Description("A template resource with a numeric ID")]
	public static ResourceContents TemplateResource(RequestContext<ReadResourceRequestParams> requestContext, int id)
	{
	int index = id - 1;
	if ((uint)index >= ResourceGenerator.Resources.Count)
	{
	throw new NotSupportedException($"Unknown resource: {requestContext.Params?.Uri}");
	}
	var resource = ResourceGenerator.Resources[index];
	return resource.MimeType == "text/plain" ?
	new TextResourceContents
	{
	Text = resource.Description!,
	MimeType = resource.MimeType,
	Uri = resource.Uri,
	} :
	new BlobResourceContents
	{
	Blob = resource.Description!,
	MimeType = resource.MimeType,
	Uri = resource.Uri,
	};
	}
	}

---

Alternatively you can use:

csharp-sdk/src/ModelContextProtocol/McpServerBuilderExtensions.cs

Lines 339 to 353 in 15f8e89

	public static IMcpServerBuilder WithResources(this IMcpServerBuilder builder, IEnumerable<McpServerResource> resourceTemplates)
	{
	Throw.IfNull(builder);
	Throw.IfNull(resourceTemplates);
	foreach (var resourceTemplate in resourceTemplates)
	{
	if (resourceTemplate is not null)
	{
	builder.Services.AddSingleton(resourceTemplate);
	}
	}
	return builder;
	}