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Exercise 4: Route Groups & Filters

Objective​

Use ASP.NET Core 7+ features: Route Groups and Endpoint Filters.

Route Groups Implementation​

var api = app.MapGroup("/api")
    .WithOpenApi();

var products = api.MapGroup("/products")
    .WithTags("Products")
    .AddEndpointFilter(async (context, next) =>
    {
        // Logging filter for all product endpoints
        Console.WriteLine($"Product endpoint called: {context.HttpContext.Request.Path}");
        return await next(context);
    });

products.MapGet("/", GetAllProducts);
products.MapGet("/{id:int}", GetProduct);
products.MapPost("/", CreateProduct);
products.MapPut("/{id:int}", UpdateProduct);
products.MapDelete("/{id:int}", DeleteProduct);

Endpoint Filters​

Validation Filter​

app.MapPost("/api/products", CreateProduct)
    .AddEndpointFilter(async (context, next) =>
    {
        var product = context.GetArgument<Product>(0);

        if (string.IsNullOrWhiteSpace(product.Name))
            return Results.BadRequest("Name is required");

        if (product.Price <= 0)
            return Results.BadRequest("Price must be positive");

        return await next(context);
    });

ID Validation Filter​

app.MapGet("/api/products/{id:int}", GetProduct)
    .AddEndpointFilter(async (context, next) =>
    {
        var id = context.GetArgument<int>(0);

        if (id <= 0)
            return Results.BadRequest("Invalid ID");

        return await next(context);
    });

Rate Limiting with Route Groups​

builder.Services.AddRateLimiter(options =>
{
    options.AddFixedWindowLimiter("api-limit", opt =>
    {
        opt.Window = TimeSpan.FromMinutes(1);
        opt.PermitLimit = 10;
    });
});

var rateLimitedApi = app.MapGroup("/api")
    .RequireRateLimiting("api-limit");

Challenge​

  1. Create separate route groups for public and authenticated endpoints
  2. Add caching filter for GET requests
  3. Implement audit logging filter
  4. Add response transformation filter

Expected Outcome​

  • Well-organized endpoints using route groups
  • Reusable endpoint filters
  • Understanding of filter execution order