checkbox in datagrid

[pleaseexplaintome]

hello, I am using C#. How do I bind a checkbox in a asp.net webform
datagrid? the oracle database has a number field where I want any non
zero value to be true, 0 is false.

I have created a template column. when I try:
<asp:CheckBox ID="chk" Runat="server"
Checked='<%#DataBinder.Eval(Container.DataItem, "duplicate")%>'/> it
errors out with "specified cast is not valid"

thanks