记录web api的request以及response(即写log)

https://www.cnblogs.com/felixnet/p/5689501.html

https://blog.csdn.net/Vblegend_2013/article/details/83446229

https://stackoverflow.com/questions/27176329/web-api-request-content-empty

https://forums.asp.net/t/2127541.aspx?Get+Http+Raw+Request+and+Response       这个里面提到了DelegatingHandler

https://www.infoworld.com/article/3211590/how-to-log-request-and-response-metadata-in-aspnet-web-api.html   这个里面提到了DelegatingHandler

https://github.com/aspnet/AspNetWebStack/issues/150

综合上面几个链接，日志应该使用delegating handler里面处理。(ActionFilter里面，http request的content已经被读取过了，需要像第一个链接里面一样，先重置回去，再读，比较麻烦)

 string requestMessage = requestContent.ReadAsStringAsync().Result; //request raw
            string responseMessage = response.ToString(); //response raw

自己写的版本

public class LogHandler : DelegatingHandler
    {
        private string _requestId;
        private readonly string _newLine = Environment.NewLine;

        protected override async Task<HttpResponseMessage> SendAsync(HttpRequestMessage request,
            CancellationToken cancellationToken)
        {
            _requestId = DateTime.Now.Ticks.ToString();
            var requestBody = request.Content.ReadAsStringAsync().Result;
            LogUtil.CreateLog(LogLevel.Message,
                $"{_requestId}{_newLine}{request.Method.Method} {request.RequestUri.AbsoluteUri} HTTP/{request.Version}{_newLine}{requestBody}");

            var response = await base.SendAsync(request, cancellationToken);
            string responseBody = response.Content.ReadAsStringAsync().Result;
            LogUtil.CreateLog(LogLevel.Message, $"{_requestId}{_newLine}HTTP/{response.Version} {(int)response.StatusCode} {response.StatusCode}{_newLine}{responseBody}{_newLine}{_newLine}");
            return response;
        }
    }

有ReadAsAsync扩展方法，自动进行类型的转换

  var apiRequest = request.Content.ReadAsAsync<ApiRequest<dynamic>>().Result;
            OwinRequestScopeContext.Current.Items["CountryCode"] = apiRequest.Header.OpCo;

这个地方如果需要重复读取数据的话

https://stackoverflow.com/questions/26942514/multiple-calls-to-httpcontent-readasasync

If you want to read again and again, you would probably want to read as stream and seek to beginning every time you read the stream.

But then if you want to do what do you now but get the second read working, you can seek to the beginning of the stream, after the first read, like this.

await httpContent.LoadIntoBufferAsync();
var X = await httpContent.ReadAsAsync<T>();

Stream stream = await httpContent.ReadAsStreamAsync();
stream.Seek(, SeekOrigin.Begin);

var Y = await httpContent.ReadAsAsync<Dictionary<string, object>>();

中间的stream不需要using，否则会遇到这种错误

HTTP/1.1 400 BadRequest
{"Message":"The request is invalid.","ModelState":{"request":["Stream was not readable."]}}