سلام این کد رو بنویسید



 <div>



<asp:ScriptManager ID="sr" runat="server"></asp:ScriptManager>

    <asp:UpdateProgress ID="pro" runat="server" AssociatedUpdatePanelID="w" DisplayAfter="1">

    <ProgressTemplate>

    </ProgressTemplate>

    </asp:UpdateProgress>

    <asp:UpdatePanel ID="w" runat="server">

    <ContentTemplate>

    <asp:TextBox ID="txt1" runat="server"></asp:TextBox>

    <asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>

    <asp:Button ID="btn" runat="server" Text="sasda" onclick="btn_Click"  />

    </ContentTemplate>

    </asp:UpdatePanel>

    

    </div>


کد درون دکمه 



  txt1.Text = string.Empty;

        TextBox1.Text = string.Empty;