when i execute the below code it is not working in server

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);

ShowEditLink(true);

lblUpdate.Text = "This image is saved";

The above code is working in local machine, but when i execute on the server error as follows

System.ComponentModel.Win32Exception: The handle is invalid

The below error shows in following line as follows

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

please help me. what is the problem in my code.

Regards,

Rao.