planforge-new-middleware

name	planforge-new-middleware
description	Scaffold ASP.NET Core middleware with request/response pipeline, DI support, structured logging, and proper ordering.
metadata	{"author":"plan-forge","source":".github/prompts/new-middleware.prompt.md"}

---

description: "Scaffold ASP.NET Core middleware with request/response pipeline, DI support, structured logging, and proper ordering." agent: "agent" tools: [read, edit, search]

Create New Middleware

Scaffold an ASP.NET Core middleware component for the HTTP request pipeline.

Required Pattern

Convention-Based Middleware

public class {Name}Middleware(
    RequestDelegate next,
    ILogger<{Name}Middleware> logger)
{
    public async Task InvokeAsync(HttpContext context)
    {
        // Pre-processing (before the next middleware)
        logger.LogDebug("{Name}Middleware executing for {Path}", context.Request.Path);

        try
        {
            await next(context);
        }
        finally
        {
            // Post-processing (after the response)
        }
    }
}

// Extension method for clean registration
public static class {Name}MiddlewareExtensions
{
    public static IApplicationBuilder Use{Name}(this IApplicationBuilder builder)
        => builder.UseMiddleware<{Name}Middleware>();
}

Scoped-Service Middleware (IMiddleware)

// Use when the middleware needs scoped services
public class {Name}Middleware(ILogger<{Name}Middleware> logger) : IMiddleware
{
    public async Task InvokeAsync(HttpContext context, RequestDelegate next)
    {
        // Access scoped services directly via constructor injection
        await next(context);
    }
}

// Must register in DI
builder.Services.AddScoped<{Name}Middleware>();

Registration Order (Program.cs)

// Order matters! Follow this sequence:
app.UseExceptionHandler();      // 1. Error handling (outermost)
app.UseCorrelationId();         // 2. Correlation ID
app.UseRequestLogging();        // 3. Request logging
app.UseAuthentication();        // 4. Authentication
app.UseAuthorization();         // 5. Authorization
app.UseRateLimiting();          // 6. Rate limiting
app.Use{Name}();                // 7. Your custom middleware

Common Middleware Types

Type	Purpose	Example
Correlation ID	Attach trace ID to every request	Read/generate X-Correlation-Id header
Tenant Resolution	Extract tenant from token/header	Set ITenantContext.TenantId
Request Logging	Log method, path, status, duration	Structured log with Serilog
Exception Handling	Map exceptions to ProblemDetails	Global try/catch with RFC 9457

Rules

• Middleware handles cross-cutting concerns ONLY — no business logic
• Always call await next(context) unless short-circuiting intentionally
• Use finally blocks for post-processing (guarantees execution on errors)
• Add an extension method Use{Name}() for clean Program.cs registration
• Use IMiddleware interface when scoped DI services are needed

Reference Files

• Security instructions
• Observability instructions
• Architecture principles