Screen capture in windows desktop service

DateTime fileCreationDatetime = DateTime.Now;
Bitmap bitmap = new Bitmap(500, 500);
Graphics graphics = Graphics.FromImage(bitmap as Image);
string fileName = string.Empty;
fileName = string.Format("{0}.jpg", fileCreationDatetime.ToString(@"yyyyMMdd") + "_" + fileCreationDatetime.ToString(@"HHmmss"));
string filePath = "C:" + "\\Image\\" + Environment.UserName + "\\" + fileCreationDatetime.ToString(@"yyyyMMdd") + "\\";

if (!Directory.Exists(filePath))
{
    Directory.CreateDirectory(filePath);
}



graphics.CopyFromScreen(25, 25, 25, 25, bitmap.Size);
bitmap.Save(filePath + fileName, ImageFormat.Jpeg);