[asp.net] ASP.Net Download file to client browser

I'm writing a simple test page to download a text file from a browser on button click. I am getting a really strange error that I have never seen before. Any thoughts?

The error occurs on Response.End(); and the file never gets to the client browser

Code:

  string filePath = "C:\\test.txt";
  FileInfo file = new FileInfo(filePath);
  if (file.Exists)
  {
    Response.ClearContent();
    Response.AddHeader("Content-Disposition", "attachment; filename=" + file.Name);
    Response.AddHeader("Content-Length", file.Length.ToString());
    Response.ContentType = "text/plain";
    Response.TransmitFile(file.FullName);
    Response.End();
  }

Error:

Unable to evaluate expression because the code is optimized or a native frame is on top of the call stack.

Just a slight addition to the above solution if you are having problem with downloaded file's name...

Response.AddHeader("Content-Disposition", "attachment; filename=\"" + file.Name + "\"");

This will return the exact file name even if it contains spaces or other characters.