Adds a minimal sample demonstrating .NET 10's file-based programs feature for MCP servers—complete server in a single .cs file, no .csproj required.

Implementation

• samples/FileBasedMcpServer/Program.cs - Complete stdio MCP server (30 lines)

  • Shebang: #!/usr/bin/env -S dotnet run --
  • Preprocessor directives: #:package and #:project for dependencies
  • Top-level statements with file-scoped EchoTool class
  • Runs directly: dotnet run Program.cs

• samples/FileBasedMcpServer/README.md - Documentation covering usage, testing examples, and file-based vs project-based tradeoffs

Example

#!/usr/bin/env -S dotnet run --
#:package Microsoft.Extensions.Hosting
#:project ../../src/ModelContextProtocol/ModelContextProtocol.csproj

using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using ModelContextProtocol.Server;

var builder = Host.CreateApplicationBuilder(args);
builder.Services.AddMcpServer()
    .WithStdioServerTransport()
    .WithTools<EchoTool>();
await builder.Build().RunAsync();

[McpServerToolType]
file class EchoTool
{
    [McpServerTool(Name = "echo")]
    public static string Echo(string message) => $"Echo: {message}";
}

Addresses modelcontextprotocol#928

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