c# - Need to log asp.net webapi 2 request and response body to a database

Question

I am using Microsoft Asp.net WebApi2 hosted on IIS. I very simply would like to log the request body (XML or JSON) and the response body for each post.

There is nothing special about this project or the controller processing the post. I am not interested in using logging frameworks like nLog, elmah, log4net, or the built-in tracing features of web API unless it is necessary to do so.

I am simply wanting to know where to put my logging code and how to get the actual JSON or XML from the incoming and outgoing request and response.

My controller post method:

public HttpResponseMessage Post([FromBody])Employee employee)
{
   if (ModelState.IsValid)
   {
      // insert employee into to the database
   }

}

Answer 1

I would recommend using a DelegatingHandler. Then you will not need to worry about any logging code in your controllers.

public class LogRequestAndResponseHandler : DelegatingHandler
{
    protected override async Task<HttpResponseMessage> SendAsync(
        HttpRequestMessage request, CancellationToken cancellationToken)
    {
        if (request.Content != null)
        {
            // log request body
            string requestBody = await request.Content.ReadAsStringAsync();
            Trace.WriteLine(requestBody);
        }
        // let other handlers process the request
        var result = await base.SendAsync(request, cancellationToken);

        if (result.Content != null)
        {
            // once response body is ready, log it
            var responseBody = await result.Content.ReadAsStringAsync();
            Trace.WriteLine(responseBody);
        }

        return result;
    }
}

Just replace Trace.WriteLine with your logging code and register the handler in WebApiConfig like this:

config.MessageHandlers.Add(new LogRequestAndResponseHandler());

Here is the full Microsoft documentation for Message Handlers.