filter a GridView column based on another column, ASP.NET

< asp:Button runat="server" ID="GoButton" Text="Go" CommandName="Select" Visible='<%# ((System.Data.DataRowView)Container.DataItem)["ABC"] != DBNull.Value %/>' />

Only String Type accpts null value in mssql db

if you want to do assign a NULL value to a integer type column, u will get error, I had to try to give a -1 value to work around, is there a better/real solution?