Bits of .NET

Middleware affects all endpoints. Endpoint Filters apply logic only to specific endpoints you choose.

Create Filter:

public class LoggingFilter : IEndpointFilter
{
    public async ValueTask InvokeAsync(
        EndpointFilterInvocationContext context, 
        EndpointFilterDelegate next)
    {
        Console.WriteLine($"Before: {context.HttpContext.Request.Path}");
        
        var result = await next(context);  // Call next filter/endpoint
        
        Console.WriteLine($"After: {context.HttpContext.Response.StatusCode}");
        return result;
    }
}

Apply to Specific Endpoint:

app.MapGet("/api/data", () => "Hello")
   .AddEndpointFilter();

// Only this endpoint gets the filter!

Inline Filter:

app.MapPost("/api/users", (User user) => Results.Created())
   .AddEndpointFilter(async (context, next) =>
   {
       // Validation
       var user = context.GetArgument(0);
       if (string.IsNullOrEmpty(user.Email))
           return Results.BadRequest("Email required");
       
       return await next(context);
   });

Use Cases: Validation, logging, auth checks, rate limiting – per endpoint!