How to access variable in file *.asp.cs to file *.asp?

Hi,
I have problem to access variabel in file *.asp.cs to file *.asp.

In file test.asp a has a gridview  like this:

<asp:GridView ID="gvUsers" runat="server" AutoGenerateColumns="False" OnRowDataBound="gvUsers_RowDataBound" OnSelectedIndexChanged="gvUsers_SelectedIndexChanged">
                    <Columns>
                        <asp:BoundField DataField="Email"  ReadOnly="True" />
                        <asp:BoundField DataField="FirstName" ReadOnly="True" /> ...