写一个ActionFilter检测WebApi接口请求和响应

我们一般用日志记录每次Action的请求和响应，方便接口出错后排查，不过如果每个Action方法内都写操作日志太麻烦，而且客户端传递了错误JSON或XML，没法对应强类型参数，请求没法进入方法内，

把日志记录操作放在一个ActionFilter即可。

[AttributeUsageAttribute(AttributeTargets.Method, Inherited = false, AllowMultiple = false)]
public class ApiActionAttribute : ActionFilterAttribute
{
    private string _requestId;
    public override void OnActionExecuting(HttpActionContext actionContext)
    {
        base.OnActionExecuting(actionContext);
        _requestId = DateTime.Now.Ticks.ToString();

        //获取请求数据  
        Stream stream = actionContext.Request.Content.ReadAsStreamAsync().Result;
        string requestDataStr = "";
        if (stream != null && stream.Length > 0)
        {
            stream.Position = 0; //当你读取完之后必须把stream的读取位置设为开始
            using (StreamReader reader = new StreamReader(stream, System.Text.Encoding.UTF8))
            {
                requestDataStr = reader.ReadToEnd().ToString();
            }
        }

        //[POST_Request] {requestid} http://dev.localhost/messagr/api/message/send {data}
        Logger.Instance.WriteLine("[{0}_Request] {1} {2}
{3}", actionContext.Request.Method.Method, _requestId, actionContext.Request.RequestUri.AbsoluteUri, requestDataStr);
    }

    public override void OnActionExecuted(HttpActionExecutedContext actionExecutedContext)
    {
        base.OnActionExecuted(actionExecutedContext);
        string responseDataStr = actionExecutedContext.Response.Content.ReadAsStringAsync().Result;
        //[POST_Response] {requestid} {data}
        Logger.Instance.WriteLine("[{0}_Response] {1}
{2}", actionExecutedContext.Response.RequestMessage.Method, _requestId, responseDataStr);
    }
}

_requestId 是用来标识请求的，根据它可以找到对应的Request与Response，便于排查。在Action上声明：

[Route("send_email")]
[HttpPost]
[ApiAction]
[ApiException]
public async Task<SendMessageResponseDto> Send(SendEmailMessageRequestDto dto)
{
    //...
}