StandardOut has not been redirected or the process hasn't started yet in C#

          Process myProcess = new Process();   
           string result = string.Empty;
          string FilePath = @"f:\";
          string FilePath = "Notepad.exe";
         
            myProcess.StartInfo.UseShellExecute = false;
            myProcess.StartInfo.FileName = FilePath+ ExeName;
            myProcess.StartInfo.CreateNoWindow = true;         
            myProcess.StartInfo.RedirectStandardOutput = true;
            myProcess.Start();
            myProcess.WaitForExit();
         
            System.IO.StreamReader ischkout = myProcess.StandardOutput;
            if(myProcess.HasExited)
            {
                string output = ischkout.ReadToEnd();
                Response.Write(output);
            }

Try setting standard output redirection before starting the process.

myProcess.StartInfo.RedirectStandardOutput = true;
myProcess.Start();