Error when filtering

[KawaUser]

I get this error when I try to filter on the first column in my grid:

is neither a DataColumn nor a DataRelation for table DefaultView.

<telerik:GridTemplateColumn HeaderStyle-HorizontalAlign="Center" HeaderText="PO #" Visible="true">

 <ItemTemplate>

<asp:Label ID="lblPONumber" Text='<%# Eval("_PONumber") %>' runat="server">
</asp:Label>
</ItemTemplate>

<HeaderStyle HorizontalAlign="Center" />

</telerik:GridTemplateColumn>

I am not sure what to give you so I am giving you the ASPX for the first column. 
Any ideas on why this error is occurring?

Thanks,
Chuck

[Elliott]

are you missing a UniqueName for the column?

[Jayesh Goyani]

Hello,

please set DataField

<telerik:GridTemplateColumn DataField="_PONumber"

Thanks,
Jayesh Goyani