fadein和fadeout似乎不起作用

Question

fadein和fadeout的效果似乎不起作用。我在ModalPopUpExtender上看过很多关于fadeIn和fadeOut的文章，并解决了之前发生的所有错误，但我仍然不知道为什么当我运行它时，我无法看到fadein和fadeout的影响。此外，没有显示错误。

这是我的.aspx代码，供您参考。

的Javascript

<script type="text/javascript">

function pageLoad() {

    $addHandler($get("showModalPopupClientButton"), 'click', showModalPopupViaClient);
    $addHandler($get("hideModalPopupViaClientButton"), 'click', hideModalPopupViaClient);
}

function showModalPopupViaClient(ev) {

    ev.preventDefault();
    var modalPopupBehavior = $find('buttonPopUp_ModalPopupExtender');
    $find("AnimationExtender1").get_OnClickBehavior().play();
    modalPopupBehavior.show();
}
function hideModalPopupViaClient(ev) {

    ev.preventDefault();
    var modalPopupBehavior = $find('buttonPopUp_ModalPopupExtender');
    modalPopupBehavior.hide();

}

</script>

HTML

<asp:Content ID="Content2" ContentPlaceHolderID="ContentPlaceHolder1" Runat="Server">
<asp:Button ID="buttonPopUp" runat="server" CssClass="hide"/>
<asp:ModalPopupExtender ID="buttonPopUp_ModalPopupExtender" runat="server" 
     DynamicServicePath="" Enabled="True" TargetControlID="buttonPopUp" BehaviorID="buttonPopUp_ModalPopupExtender"
     PopupControlID="PopUp" BackgroundCssClass="modalBackground" DropShadow="true" >
</asp:ModalPopupExtender>
  <asp:AnimationExtender ID="AnimationExtender1" runat="server" TargetControlID="FadeIn">
    <Animations>
            <OnClick>
                <Sequence AnimationTarget="PopUp">                
                    <FadeIn Duration="1" MinimumOpacity="0" MaximumOpacity="1" />
                </Sequence>
            </OnClick>

        </Animations>
    </asp:AnimationExtender>
    <asp:AnimationExtender ID="AnimationExtender2" runat="server" TargetControlID="FadeIn">
    <Animations>
            <OnClick>
                <Sequence AnimationTarget="PopUp">                
                    <FadeOut Duration="1" MinimumOpacity="0" MaximumOpacity="1" />
                </Sequence>
            </OnClick>

        </Animations>
    </asp:AnimationExtender>
    <asp:HiddenField runat="server" ID="FadeIn" />
 </p>
 <div id="PopUp">
    <div id="ImagePopUp"> 
    <asp:Image ID="Image4" runat="server" Height="260px" Width="352px" />
    </div>  
<asp:Label ID="packageName" CssClass="PopUpDeco" runat="server" Text=""></asp:Label>
</div>