asp.net + vb.net + gridview

Question

When i run the web application, i got the message :

Control 'gridView' of type 'GridView' must be placed inside a form tag with runat=server.

Then i checked the source, i had got this code :

<form id="form1" runat="server">

<asp:GridView ID="gridView" runat="Server">

</asp:GridView>

</form>

So, very very pls tell me how i have to do?