MemberShip ile kullanıcının giriş iznini belirleme.

...
<Columns>
   <asp:BoundField DataField="UserName" HeaderText="UserName" />
   <asp:BoundField DataField="Email" HeaderText="Email" />
   <asp:TemplateField HeaderText="IsApproved" ShowHeader="False">
   <ItemTemplate>
   <asp:LinkButton ID="LinkButton1" runat="server" CausesValidation="false"
CommandName="setAppr" CommandArgument='<%# Eval("UserName") %>' Text='<%# Eval("IsApproved") %>'></asp:LinkButton>
   </ItemTemplate>
   <ItemStyle HorizontalAlign="Center" />
</asp:TemplateField>

protected void GridView1_RowCommand(object sender, GridViewCommandEventArgs e)
{
   if (e.CommandName == "setAppr")
   {
      MembershipUser us = Membership.GetUser(e.CommandArgument.ToString());
      us.IsApproved = !us.IsApproved;
      Membership.UpdateUser(us);
      ...
   }
}