C# SDK MCP — Anwendungsfälle, Installieren & Live-Demo

Warum nutzen

Hauptfunktionen

First-party, co-maintained with Microsoft
Attribute-based tool registration — ASP.NET-style
Native DI, IHostedService, ILogger integration
Stdio + HTTP/SSE transports out of the box

Live-Demo

In der Praxis

csharp-sdk.replay ▶ bereit

0/0

Installieren

Wählen Sie Ihren Client

~/Library/Application Support/Claude/claude_desktop_config.json · Windows: %APPDATA%\Claude\claude_desktop_config.json

{
  "mcpServers": {
    "csharp-sdk": {
      "command": "dotnet",
      "args": [
        "run",
        "--project",
        "./MyMcpServer"
      ]
    }
  }
}

Öffne Claude Desktop → Settings → Developer → Edit Config. Nach dem Speichern neu starten.

~/.cursor/mcp.json · .cursor/mcp.json

{
  "mcpServers": {
    "csharp-sdk": {
      "command": "dotnet",
      "args": [
        "run",
        "--project",
        "./MyMcpServer"
      ]
    }
  }
}

Cursor nutzt das gleiche mcpServers-Schema wie Claude Desktop. Projektkonfiguration schlägt die globale.

VS Code → Cline → MCP Servers → Edit

{
  "mcpServers": {
    "csharp-sdk": {
      "command": "dotnet",
      "args": [
        "run",
        "--project",
        "./MyMcpServer"
      ]
    }
  }
}

Klicken Sie auf das MCP-Servers-Symbol in der Cline-Seitenleiste, dann "Edit Configuration".

~/.codeium/windsurf/mcp_config.json

{
  "mcpServers": {
    "csharp-sdk": {
      "command": "dotnet",
      "args": [
        "run",
        "--project",
        "./MyMcpServer"
      ]
    }
  }
}

Gleiche Struktur wie Claude Desktop. Windsurf neu starten zum Übernehmen.

~/.continue/config.json

{
  "mcpServers": [
    {
      "name": "csharp-sdk",
      "command": "dotnet",
      "args": [
        "run",
        "--project",
        "./MyMcpServer"
      ]
    }
  ]
}

Continue nutzt ein Array von Serverobjekten statt einer Map.

~/.config/zed/settings.json

{
  "context_servers": {
    "csharp-sdk": {
      "command": {
        "path": "dotnet",
        "args": [
          "run",
          "--project",
          "./MyMcpServer"
        ]
      }
    }
  }
}

In context_servers hinzufügen. Zed lädt beim Speichern neu.

claude mcp add csharp-sdk -- dotnet run --project ./MyMcpServer

Einzeiler. Prüfen mit claude mcp list. Entfernen mit claude mcp remove.

Anwendungsfälle

Praxisnahe Nutzung: C# SDK

Build an MCP server in .NET that exposes your existing services

👤 C#/.NET engineers with internal APIs ⏱ ~45 min intermediate

Wann einsetzen: You're on .NET and want to expose business logic to agents without a rewrite.

Voraussetzungen

.NET 8+ SDK — dotnet --version

Ablauf

Create the project

dotnet new console -n MyMcpServer. Add ModelContextProtocol NuGet. Use the minimal hosting template for MCP.✓ Kopiert

→ csproj + Program.cs with MCP hosted service
Add a tool

Create a static class with [McpServerToolType]. Add a method GetOrder(string id) decorated with [McpServerTool(Description="...")] that calls my existing OrderService via DI.✓ Kopiert

→ Tool compiles, description comes from attribute
Test with the inspector

Run the server as stdio. Launch the MCP Inspector via npx @modelcontextprotocol/inspector dotnet run. Call GetOrder.✓ Kopiert

→ Tool invocation returns order JSON

Ergebnis: A compiled, typed MCP server reusing your existing .NET services and DI container.

Fallstricke

Tool methods that are instance methods on a class need DI to work — Register the owning class in the ServiceCollection; the SDK resolves through DI
Async methods without proper cancellation tokens hang at shutdown — Accept CancellationToken ct as the last parameter on every tool — SDK injects it

Build a .NET console app that uses MCP servers

👤 C# devs building internal automation ⏱ ~30 min intermediate

Wann einsetzen: You want deterministic .NET code (not an LLM loop) that calls MCP servers — e.g., a scheduled job that uses github + filesystem MCPs.

Ablauf

Add the client package

Create a console app. Reference ModelContextProtocol client. Add a config pointing at a stdio server (e.g. npx -y @modelcontextprotocol/server-github).✓ Kopiert

→ Client builds
Connect and call

Start the client, list tools, call list_repositories with my org name. Print the result.✓ Kopiert

→ Repos printed to console
Wrap as a scheduled job

Turn this into a Worker Service that runs nightly. Log metrics via ILogger.✓ Kopiert

→ Worker runs via dotnet run and schedules cleanly

Ergebnis: MCP as a library, not just a chat plugin — works inside any .NET process.

Fallstricke

Stdio servers take time to start, first call times out — Initialize the client at app startup and reuse; don't spawn per-call

Serve an MCP endpoint from an ASP.NET Core app

👤 .NET platform engineers ⏱ ~60 min advanced

Wann einsetzen: You want the MCP server hosted inside an existing ASP.NET Core service, behind the same auth and ingress.

Voraussetzungen

Existing ASP.NET Core app or willingness to start one — dotnet new web

Ablauf

Add MCP services + endpoint

In Program.cs, builder.Services.AddMcpServer().WithToolsFromAssembly(). Then app.MapMcp('/mcp').✓ Kopiert

→ /mcp endpoint responds to SSE handshake
Share auth with the rest of the app

Put the /mcp endpoint behind my existing JWT bearer auth middleware. Verify unauth'd requests get 401.✓ Kopiert

→ 401 unauth, 200 auth
Deploy and connect

Deploy. Wire a teammate's Claude Desktop via mcp-remote https://myapp.com/mcp with their JWT.✓ Kopiert

→ Team members see tools

Ergebnis: MCP alongside your existing API in one deploy with one auth story.

Fallstricke

Kestrel buffers SSE responses behind a reverse proxy — Disable response buffering; ensure IIS/nginx/Cloudflare in front also disable buffering for /mcp

Kombinieren mit: cloud-run

Kombinationen

Mit anderen MCPs für 10-fache Wirkung

csharp-sdk + cloud-run

Deploy .NET MCP server on Cloud Run alongside other microservices

Containerize my .NET MCP server (mcr.microsoft.com/dotnet/aspnet base), deploy to Cloud Run with a min-instance=1 for cold-start mitigation.✓ Kopiert

csharp-sdk + fastmcp

Comparison for polyglot shops — different SDKs, same protocol

Our team has both Python and .NET services. Use FastMCP for Python APIs and csharp-sdk for .NET APIs — both behind one ContextForge gateway.✓ Kopiert

Werkzeuge

Was dieses MCP bereitstellt

Werkzeug	Eingaben	Wann aufrufen	Kosten
[McpServerToolType]	attribute on a class	Mark classes whose methods should be exposed	free
[McpServerTool(Description)]	attribute on a method	Each method you want agents to call	free
AddMcpServer() / WithToolsFromAssembly()	fluent builder	Program.cs at startup	free
MapMcp('/path')	ASP.NET endpoint	ASP.NET hosting only	free
IMcpClient	stdio or SSE transport config	Client-side usage	free

Kosten & Limits

Was der Betrieb kostet

API-Kontingent: None — this is an SDK
Tokens pro Aufruf: No framework overhead beyond MCP protocol
Kosten in €: Free, MIT licensed
Tipp: Use .NET's built-in logging and HealthChecks to catch problems before they balloon in prod

Sicherheit

Rechte, Secrets, Reichweite

Credential-Speicherung: Standard .NET: user-secrets for dev, environment variables or Key Vault for prod

Datenabfluss: Whatever your tools reach

Fehlerbehebung

Häufige Fehler und Lösungen

Tool not appearing in inspector

WithToolsFromAssembly() only scans the executing assembly. For tools in referenced libraries, pass the Assembly explicitly: WithTools(typeof(MyTools).Assembly).

DI can't resolve my service in a tool method

Tool types must be registered in the container. Add builder.Services.AddScoped<OrderService>() before AddMcpServer.

ASP.NET MapMcp returns 404

You mapped after app.Run() — move MapMcp before Run. Also check the path doesn't conflict with other endpoints.

JSON serialization fails on enums

SDK uses System.Text.Json; add [JsonStringEnumConverter] on your enums or configure globally.

Alternativen

C# SDK vs. andere

Alternative	Wann stattdessen	Kompromiss
FastMCP (Python)	You're OK picking up Python — richer example ecosystem	Different language; team skill dependent
TypeScript MCP SDK	Node / TS shop	Similar DX, language choice

Mehr

Ressourcen

📖 Offizielle README auf GitHub lesen

🐙 Offene Issues ansehen

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