ASP-NET-Core中间件管道

1. 管道模型

Request → Middleware1 → Middleware2 → Middleware3 → Endpoint
                                                    ↓
Response ← Middleware1 ← Middleware2 ← Middleware3 ← Handler

2. 内置中间件

var app = builder.Build();

app.UseHttpsRedirection();
app.UseStaticFiles();
app.UseRouting();
app.UseAuthentication();
app.UseAuthorization();
app.MapControllers();

3. 自定义中间件

app.Use(async (context, next) => {
    // 前置逻辑
    var sw = Stopwatch.StartNew();

    await next();  // 调用下一个中间件

    // 后置逻辑
    sw.Stop();
    context.Response.Headers.Add("X-Elapsed-Ms", sw.ElapsedMilliseconds.ToString());
});

4. 中间件顺序

顺序很重要！错误的顺序可能导致功能异常：

1. UseExceptionHandler / UseDeveloperExceptionPage
2. UseHsts
3. UseHttpsRedirection
4. UseStaticFiles
5. UseRouting
6. UseCors
7. UseAuthentication
8. UseAuthorization
9. MapControllers