I just had the same problem and got it to work like this, using the image control (named imgMfgNameBarcode). Still testing it but seems to work.
using Zen.Barcode;
Code39BarcodeDraw barcode39 = BarcodeDrawFactory.Code39WithoutChecksum;
lblMfgName.Content = "BinOptics Corporation";
sTest = lblMfgName.Content.ToString();
System.Drawing.Image img =
barcode39.Draw(lblMfgName.Content.ToString(), 40, 2);
BitmapImage bi = new BitmapImage();
bi.BeginInit();
MemoryStream ms = new MemoryStream();
img.Save(ms, ImageFormat.Bmp);
ms.Seek(0, SeekOrigin.Begin);
bi.StreamSource = ms;
bi.EndInit();
imgMfgNameBarcode.Source = bi;