when execute the below code in server it is not working

See more:

C#

My code as follows

Bitmap bitmap = new Bitmap(990, 540);
Graphics graphics = Graphics.FromImage(bitmap as System.Drawing.Image);
graphics.CopyFromScreen(5, 160, 0, 0, bitmap.Size);
bitmap.Save(@"c:\\" + ddlSession.Text.ToString().Trim() + "DailySchedule.bmp", ImageFormat.Bmp);
lblUpdate.Text = "This image is saved";

When i execute the above code in local machine it is working, but when i execute the above code in server error as follows
System.ComponentModel.Win32Exception: The handle is invalid.Error shows in below line as follows

graphics.CopyFromScreen(5, 160, 0, 0, bitmap.Size);

Please help me. What is the problem in my code.

Regards
Narasiman P.