c# Log4Net not logging the real line where exception happens

Question

I have a c# controller and inside a method I have code with a try catch statement:

My controller has a top level class attribute LogAttribute:

public class LogAttribute : HandleErrorAttribute
{
    public ILogManager Logger { get; set; }

    public override void OnException(ExceptionContext filterContext)
    {
        Exception exception = filterContext.Exception;
        filterContext.ExceptionHandled = true;

        /* start log error */
        var logHelper = new Helpers.LogHelper (this.Logger);
        Guid errorUid = Guid.NewGuid();

        // call log4net
        logHelper.LogErrorString(errorUid, exception);
        /* end log error */
     }

}

[Log]
public class TestController 
{
   public JsonResult TestMethod(){

       try{

           //...some code here

           List<string> list = null;

           //Line 65 force expection Object reference not set to an instance of an object
           list.count(); 

       } 
       catch(Exception ex) {


           // ... do some code here

           throw ex; // Line 82
       }

      return null;
   }
}

The Log4Net logging is working fine but when I debug just after the catch and see the Exception ex I can see that the StackTrace line is the 65 as the exception line, and this is totally correct because is where the exception happened. But when Log4Net logs the error it shows as lines 82 that is exactly where I manually trhow the exception.

** UPDATE **

I just checked that the excepction StackTrace is correct in the Catch statement but exactly when the MVC Log attribute OnException handler catch that then the stacktrace is being reset. So is problem of the OnException method.

Any clue?