Here is another easy solution i have figured out:
Bitmap bp=new Bitmap(dataGridView1.Width,dataGridView1.Height);
dataGridView1.DrawToBitmap(bp,new Rectangle(0,0,dataGridView1.Width,dataGridView1.Height));
Bitmap bp1 = bp.Clone(new Rectangle(50, 50, 100, 100), System.Drawing.Imaging.PixelFormat.DontCare);
bp1.Save("test2.jpg", System.Drawing.Imaging.ImageFormat.Jpeg);
the cords of rectangle passed in second bitmap will crop the complete image to ur required size and u will have only cropped portion u needed.