I’ve been using the sample from the asp.net website to log unhandled exceptions using the IExceptionLogger interface.
using System;
using System.Net.Http;
using System.Web;
using System.Web.Http.ExceptionHandling;
namespace Elmah.Server.ExceptionHandling
{
public class ElmahExceptionLogger : ExceptionLogger
{
private const string HttpContextBaseKey = "MS_HttpContext";
public override void Log(ExceptionLoggerContext context)
{
// Retrieve the current HttpContext instance for this request.
HttpContext httpContext = GetHttpContext(context.Request);
if (httpContext == null)
{
return;
}
// Wrap the exception in an HttpUnhandledException so that ELMAH can capture the original error page.
Exception exceptionToRaise = new HttpUnhandledException(message: null, innerException: context.Exception);
// Send the exception to ELMAH (for logging, mailing, filtering, etc.).
ErrorSignal signal = ErrorSignal.FromContext(httpContext);
signal.Raise(exceptionToRaise, httpContext);
}
private static HttpContext GetHttpContext(HttpRequestMessage request)
{
HttpContextBase contextBase = GetHttpContextBase(request);
if (contextBase == null)
{
return null;
}
return ToHttpContext(contextBase);
}
private static HttpContextBase GetHttpContextBase(HttpRequestMessage request)
{
if (request == null)
{
return null;
}
object value;
if (!request.Properties.TryGetValue(HttpContextBaseKey, out value))
{
return null;
}
return value as HttpContextBase;
}
private static HttpContext ToHttpContext(HttpContextBase contextBase)
{
return contextBase.ApplicationInstance.Context;
}
}
}
I recently changed a WebAPI application to use OWIN and later found my logging stopped working. OWIN may not have been to blame but it sure looked guilty.
Debugging through, I noticed that the Properties collection of the ExceptionLoggerContext.Request didn’t contain the MS_HttpContext key. I noticed the Elmah ErrorSignal class had a static class FromCurrentContext as well as the method in use FromContext(HttpContext context) which takes in the MS_HttpContext.
internal class GlobalExceptionLogger : ExceptionLogger
{
private static readonly ILog Log4Net = LogManager.GetLogger(System.Reflection.MethodBase.GetCurrentMethod().DeclaringType);
public override void Log(ExceptionLoggerContext context)
{
Log4Net.Error(String.Format("Unhandled exception thrown in {0} for request {1}: {2}",
context.Request.Method, context.Request.RequestUri, context.Exception));
}
}
public class ElmahExceptionLogger : ExceptionLogger
{
public override void Log(ExceptionLoggerContext context)
{
// Wrap the exception in an HttpUnhandledException so that ELMAH can capture the original error page.
Exception exceptionToRaise = new HttpUnhandledException(message: null, innerException: context.Exception);
// Send the exception to ELMAH (for logging, mailing, filtering, etc.).
ErrorSignal signal = ErrorSignal.FromCurrentContext();
signal.Raise(exceptionToRaise);
}
}
The logging is now working.
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