try
{
  WebRequest webRequest = WebRequest.Create("http://www.csdn.net");
  WebResponse response = await webRequest.GetResponseAsync();
  // ...
}
catch (WebException exception)
{
  await WriteErrorToLog(exception);
}try
{
    DoSomeHttpRequest();
}
catch (System.Web.HttpException e) if (e.GetHttpCode() == 400)
{
    WriteLine("Not Found");
}
catch (System.Web.HttpException e) if (e.GetHttpCode() == 500)
{
    WriteLine("Internal Server Error");
}
catch
{
    WriteLine("Generic Error");
}try
{
    DoSomeHttpRequest();
}
catch (System.Web.HttpException e)
{
    switch (e.GetHttpCode())
    {
        case 400:
            WriteLine("Bad Request");
        case 500:
            WriteLine("Internal Server Error");
        default:
            WriteLine("Generic Error");
    }
}C# 6.0 (C# vNext) 新功能之:Exception-Handling Improvements
原文:http://blog.csdn.net/kendo3065/article/details/40085319