Follow this :
<asp:ScriptManager ID="ScriptManager1" runat="server"></asp:ScriptManager>
<asp:UpdatePanel ID="UpdatePanel1" runat="server">
<ContentTemplate>
<asp:TextBox ID="TextBox1" runat="server" TextMode="MultiLine" ></asp:TextBox>
<asp:Button ID="Button1" runat="server" Text="btn" onclick="Button1_Click" /><br />
<asp:GridView ID="GridView1" runat="server"></asp:GridView>
</ContentTemplate>
</asp:UpdatePanel>
Hope it will help you.
Don't forget to mark as answer if it helps. :)