<form id="form1" runat="server" DefaultFocus="formVw$txtName">
<div>
<asp:FormView ID="formVw" runat="server">
<ItemTemplate>
Name:
<asp:TextBox ID="txtName" runat="server"
Text='<%# Eval("FirstName") " " Eval("LastName") %>' />
</ItemTemplate>
</asp:FormView>
</div>
</form>

TextBox tb = this.FindControl("form1$formVw$txtName") as TextBox;
if (tb != null)
{
//Access TextBox control
}

<form id="form1" runat="server">
Search Text: <asp:TextBox ID="txtSearch" runat="server" />
<asp:RequiredFieldValidator ID="valSearch" runat="Server"
ControlToValidate="txtSearch" ValidationGroup="SearchGroup" />
<asp:Button ID="btnSearch" runat="server" Text="Search"
ValidationGroup="SearchGroup" />
....
Other controls with validators and buttons defined here
</form>