GEnerated Barcode dont scan in barcode scanner?

hi any help, i dont know what is the problem why i cant scan the barcode i created in a barcode scanner? here is my code..

//barcode
string barCode = s_refnum;
System.Web.UI.WebControls.Image imgBarCode = new System.Web.UI.WebControls.Image();
using (Bitmap bitMap = new Bitmap(barCode.Length * 35, 80))
{
using (Graphics graphics = Graphics.FromImage(bitMap))
{
System.Drawing.Font oFont = new System.Drawing.Font("IDAutomationHC39M", 16);
PointF point = new PointF(2f, 2f);
SolidBrush blackBrush = new SolidBrush(System.Drawing.Color.Black);
SolidBrush whiteBrush = new SolidBrush(System.Drawing.Color.White);
graphics.FillRectangle(whiteBrush, 0, 0, bitMap.Width, bitMap.Height);
graphics.DrawString(barCode, oFont, blackBrush, point);
Response.ContentType = "image/jpeg";
string s_path = Server.MapPath("images/barcode/" + s_refnum + ".jpeg");
bitMap.Save(s_path, ImageFormat.Jpeg);
...