Save a ZedGraph as a picture in vb.net

Dim objBitmap As Bitmap = New Bitmap(850, 1100)
Dim g As Graphics = Graphics.FromImage(objBitmap)
Public PB As System.Windows.Forms.PictureBox
PB.Image = ZedGraphControlA.GetImage()
g.DrawImage(PB.Image, 0, 747)
objBitmap.Save("c:\Graph.jpg", System.Drawing.Imaging.ImageFormat.Jpeg)