<form id="form1" runat="server">
<asp:TextBox ID="txtCode" runat="server"></asp:TextBox>
<asp:Button ID="btnGenerate" runat="server" Text="Generate" onclick="btnGenerate_Click" />

<hr />

<asp:PlaceHolder ID="plBarCode" runat="server" />
</form>

 
Imports System.Drawing
Imports System.Drawing.Imaging
Imports System.IO

Protected Sub btnGenerate_Click(sender As Object, e As EventArgs)
    Dim barCode As String = txtCode.Text
    Dim imgBarCode As New System.Web.UI.WebControls.Image()
    Using bitMap As New Bitmap(barCode.Length * 40, 80)
        Using graphics__1 As Graphics = Graphics.FromImage(bitMap)
            Dim oFont As New Font("IDAutomationHC39M", 16)
            Dim point As New PointF(2.0F, 2.0F)
            Dim blackBrush As New SolidBrush(Color.Black)
            Dim whiteBrush As New SolidBrush(Color.White)
            graphics__1.FillRectangle(whiteBrush, 0, 0, bitMap.Width, bitMap.Height)
            graphics__1.DrawString("*" & barCode & "*", oFont, blackBrush, point)
        End Using
        Using ms As New MemoryStream()
            bitMap.Save(ms, System.Drawing.Imaging.ImageFormat.Png)
            Dim byteImage As Byte() = ms.ToArray()
 
            Convert.ToBase64String(byteImage)
            imgBarCode.ImageUrl = "data:image/png;base64," & Convert.ToBase64String(byteImage)
        End Using
        plBarCode.Controls.Add(imgBarCode)
    End Using
End Sub

https://www.aspsnippets.com/Articles/Dynamically-Generate-and-Display-Barcode-Image-in-ASPNet.aspx