Add CommandName for each button in the gridview and
use grdCardWallet_RowCommand to do your operation as required.
<asp:TemplateField ItemStyle-VerticalAlign="Middle">
<ItemTemplate>
<asp:LinkButton ID="lnkApprove"
Text="Approve" CommandArgument='<%# Eval("Approve") %>' CommandName="Arrpove"
runat="server"></asp:LinkButton>
<div class="ht4">
</div>
<asp:LinkButton ID="lnkReject" CommandName="Reject" CommandArgument='<%# Eval("Reject") %>'
Text="Reject" runat="server"></asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
use the below codebehind for your action
protected void grid_RowCommand(object sender, GridViewCommandEventArgs e)
{
if (e.CommandName == "Aprove")
{
}
if (e.CommandName == "reject")
{
}
}