.NET Core 7 Minimal API：通用过滤器中如何区分服务与POST请求体

我正在使用.NET Core 7 Minimal API，需要记录POST请求的请求体。当前代码通过给请求体DTO添加自定义RequestBodyAttribute来识别请求体，但这种方式容易因遗漏标记出错；通过参数位置判断也有风险；想通过检查[FromBody]特性来识别，但不知道在过滤器中如何获取该信息。现有代码如下：

端点配置 #

var endpoints = app.MapGroup("api/v1")
    .AddEndpointFilter<RequestResponseLogFilter>();

endpoints.MapPost("/endpoint", async ([FromServices] ServiceA serviceA, [FromServices] ServiceB serviceB, [FromBody] MyRequest request) =>
    await MyEndpoint.DoSomething(serviceA, serviceB, request));

自定义特性与DTO #

public class RequestBodyAttribute : Attribute
{
}

[RequestBody]
public class MyRequest
{
}

现有日志过滤器 #

public class RequestResponseLogFilter : IEndpointFilter
{
    public async ValueTask<object?> InvokeAsync(EndpointFilterInvocationContext context, EndpointFilterDelegate next)
    {
        var httpContext = context.HttpContext;
        var logger = httpContext.RequestServices.GetService<ILogger>()!;

        object? requestBody = context.Arguments.FirstOrDefault(a => a?.GetType().GetCustomAttribute<RequestBodyAttribute>() != null);

        logger.Information("{@Request}", LogHelper.PrepareRequest(httpContext, requestBody));

        var stopwatch = Stopwatch.StartNew();
        var result = await next(context);
        stopwatch.Stop();

        logger.Information("{@Response}", LogHelper.PrepareResponse(httpContext, result, stopwatch.Elapsed));
        return result;
    }
}

可以通过EndpointFilterInvocationContext的MethodInfo获取端点方法的参数元数据，结合[FromBody]特性精准定位请求体参数，无需额外标记或依赖参数位置。修改后的过滤器代码如下：

using Microsoft.AspNetCore.Mvc;
using System.Reflection;

public class RequestResponseLogFilter : IEndpointFilter
{
    public async ValueTask<object?> InvokeAsync(EndpointFilterInvocationContext context, EndpointFilterDelegate next)
    {
        var httpContext = context.HttpContext;
        var logger = httpContext.RequestServices.GetService<ILogger>()!;

        // 获取方法参数信息，匹配带[FromBody]特性的参数
        var methodParams = context.MethodInfo.GetParameters();
        object? requestBody = null;
        for (int i = 0; i < methodParams.Length; i++)
        {
            if (methodParams[i].GetCustomAttribute<FromBodyAttribute>() != null)
            {
                requestBody = context.Arguments[i];
                break; // 通常POST请求只有一个FromBody参数，找到后直接跳出
            }
        }

        logger.Information("{@Request}", LogHelper.PrepareRequest(httpContext, requestBody));

        var stopwatch = Stopwatch.StartNew();
        var result = await next(context);
        stopwatch.Stop();

        logger.Information("{@Response}", LogHelper.PrepareResponse(httpContext, result, stopwatch.Elapsed));
        return result;
    }
}

说明 #

• 利用context.MethodInfo.GetParameters()获取端点方法的所有参数元数据，遍历每个参数检查是否带有[FromBody]特性
• 通过参数索引对应到context.Arguments中的实参，精准获取请求体对象
• 无需给DTO添加任何自定义特性，也不依赖参数位置，完全基于ASP.NET Core原生的参数绑定特性判断，避免遗漏或位置错误的问题

内容的提问来源于stack exchange，提问作者Pavel