たとえば、 <asp:Label ID="Label1" /> <ajaxToolkit:PopupControlExtender TargetControlID="Label1" PopupControlID="Panel1" /> <asp:Button /> <asp:Panel ID="Panel1"> <asp:UpdatePanel><ContentTemplate> <asp:TextBox OnChanged="TextBox1_Changed" AutoPostback="True" /> </ContentTemplate></asp:UpdatePanel> </asp:panel></asp:button></ajaxtoolkit:popupcontrolextender></asp:label>