checking for null in gridview

Hello everyone I have this markup:
<asp:HyperLink ID="Test" runat="server" Visible='<%# if(Eval("TestID").ToString()<>Session("ID").ToString(),true, false) %>' Text='<%# Eval("Test") %>' NavigateUrl='<%# "~/Test?ID=" + HttpUtility.UrlEncode(EncryptFn(Eval("TestID"))) %>'></asp:HyperLink> I usually get error when TestID is null. This is because of the encrypt function which needs TestID to property encrypt. Is there a way I can check or stop the encryption when testID is null.

thanks. 




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