<asp:GridView ID="grdenqsup" runat="server" Width="94%" OnPageIndexChanging="grdenqsup_PageIndexChanging" PageSize="8" AllowPaging="true" AutoGenerateColumns="false">
           <RowStyle BackColor="#EFF3FB" />
           <FooterStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
           <HeaderStyle BackColor="#507CD1" Font-Bold="True" ForeColor="White" />
           <AlternatingRowStyle BackColor="White" />

        <asp:BoundField DataField="TEMP_SUPPCODE" HeaderText="SUPPLIER CODE" />
        <asp:BoundField DataField="SUPPLIERNAME" HeaderText="SUPPLIER NAME" />
        <%--<asp:BoundField DataField="SUPPLIERTITLE" HeaderText="SUPPLIER TITLE" />--%>
        <asp:BoundField DataField="SUPPLIER_ADDRESS1" HeaderText="SUPPLIER ADDRESS1" />
       <%-- <asp:BoundField DataField="SUPPLIER_ADDRESS2" HeaderText="SUPPLIER ADDRESS2" />
        <asp:BoundField DataField="SUPPLIER_PLACE" HeaderText="SUPPLIER PLACE" />--%>
         <asp:TemplateField ItemStyle-Width="40" ItemStyle-HorizontalAlign="Right" >
            <asp:TextBox ID="txtSupplier" runat="server">

            `how to use the textindex change for this txtsupplier`

I would believe that the easiest approach is not to try to create a solution to search against the gridview, but simply use the same datasource that populated the gridview. In other words, when a user types in a word or phrase into the textbox, on the click event (server side), perform a query against that same datasource with a where clause using the data from the textbox. You can do this with one datasource.

Asp.net language is very useful nowdays because it used in web development