How I can make to search in data of gridview?

Hi, 
I want to make search engine for my website. I added this codes. It is searching but if there isn't a data , it doesn't see any warring. Please look at the following codes: 

<input type="submit" value="SEARCH" />
<asp:TextBox type="search" runat="server" ID="text1" AutoCompleteType="Disabled" placeholder="Arama" value=""/></asp:textbox>
&nbsp;&nbsp;&nbsp;
<asp:RequiredFieldValidator
ID="RequiredFieldValidator1" runat="server"
ErrorMessage="ERROR !" BackColor="White"
ControlToValidate="text1" Font-Size="14px" ForeColor="Red"></asp:RequiredFieldValidator></form>
<asp:GridView ID="GridView1" AllowPaging="true" PageSize="20" runat="server"
onpageindexchanging="GridView1_PageIndexChanging">
</asp:GridView>


How i can provide to give a warring?

Regards...