You can pass semicolon separated values as command argument and then split the string and use it.
<asp:TemplateField ShowHeader="false">
<ItemTemplate>
<asp:LinkButton ID="lnkCustomize" Text="Customize" CommandName="Customize" CommandArgument="<%#Eval("IdTemplate") + ";" +Eval("EntityId")%>" runat="server">
</asp:LinkButton>
</ItemTemplate>
</asp:TemplateField>
at server side
protected void gridview_RowCommand(object sender, GridViewCommandEventArgs e)
{
string[] arg = new string[2];
arg = e.CommandArgument.ToString().Split(';');
Session["IdTemplate"] = arg[0];
Session["IdEntity"] = arg[1];
Response.Redirect("Samplepage.aspx");
}