How to generate barcode by selecting code39 from dropdown

Question

my .aspx page

 

<%@ Register Assembly="BarcodeLib.Barcode.ASP.NET" Namespace="BarcodeLib.Barcode.ASP.NET" TagPrefix="cc1" %>
 

<cc1:LinearASPNET ID="LinearASPNET1" runat="server" Type="CODE39" />

With the above code barcode image is just displayed, but my requirement is this to generate barcode value from dropdown selection and and then get its value and image to store and retrieve in database.

I means how to get barcode value and image? for example a textbox with id=txtName, then we store it value  as somevar = txtName.Text.ToString();