未触发按钮单击事件，并且首次加载页面时回发为false，asp.net

我是ASP.Net新手。我正在使用VS2010和Targeting.NET4.0框架。我正在使用ajaxtoolkit，我的站点支持ajax。我有个奇怪的问题。我没有收到服务器按钮单击事件的第一次按钮单击几次。在此内部页面加载期间，回发属性为false。有趣的是，如果导航到我的网站的任何其他页面，然后返回并执行相同的操作，则一切正常（意味着我得到了按钮单击事件）。我不知道第一次出了什么问题。另一件有趣的事情是，如果我从我的机器（运行IIS的计算机）进行测试，就不会有问题。但是这个问题可以通过另一台计算机上的浏览器来解决。我只是坐着，没有任何线索。有人能帮我吗

我的代码如下。由于版权问题，我不能给出完整的源代码。我完全被这个问题打动了。请帮帮我

<%@ Page Title="TestPage" Language="C#" MasterPageFile="~/MenuMaster.master" AutoEventWireup="true"
    CodeBehind="TestPage.aspx.cs" Inherits="TestApp"
    EnableEventValidation="false" 
 %>

<%@ Register Assembly="AjaxControlToolkit" Namespace="AjaxControlToolkit" TagPrefix="ajaxToolkit" %>

<asp:Content ID="BodyContent" runat="server" ContentPlaceHolderID="ControlContent">
    <div class="controlWrapper">
        <div class="controlLabel">
            <asp:Label ID="lblProductGroup" runat="server" Text="ProductGroup></asp:Label>
        </div>
        <div class="controlValue1">
            <asp:DropDownList ID="cmbProductGroup" runat="server" Width="120px">
            </asp:DropDownList>
        </div>
    </div>
    <div class="controlWrapper">
        <div class="controlLabel">
            <asp:Label ID="lblProduct" runat="server" Text="Product"></asp:Label>
        </div>
        <div class="controlValue1">
            <asp:DropDownList ID="cmbProduct" runat="server" Width="120px">
            </asp:DropDownList>
        </div>
    </div>
    <div class="controlWrapper">
        <div class="controlLabel">
            <asp:Label ID="lblSvcOptName" runat="server" Text="Option"></asp:Label>
        </div>
        <div class="controlValue1">
            <asp:DropDownList ID="cmbSvcOption" runat="server" Width="120px">
            </asp:DropDownList>
        </div>
        <div class="controlValue2">
            <asp:Button ID="btnAddToCart" runat="server" Text="Add To Cart" OnClick="btnAddToCart_Click" />
        </div>
    </div>
    <ajaxToolkit:CascadingDropDown ID="CascadingDropDownForProductGroup" runat="server" TargetControlID="cmbProductGroup"
        Category="ProductGroup" LoadingText="[Loading ProductGroup...]" ServiceMethod="GetDropDownContentsBasedOnSelection" />
    <ajaxToolkit:CascadingDropDown ID="CascadingDropDownForProduct" runat="server" TargetControlID="cmbProduct"
        Category="Product" LoadingText="[Loading Products...]" ServiceMethod="GetDropDownContentsBasedOnSelection"
        ParentControlID="cmbProductGroup" />
    <ajaxToolkit:CascadingDropDown ID="CascadingDropDownForSvcOptions" runat="server"
        TargetControlID="cmbSvcOption" Category="Option" LoadingText="[Loading Options...]"
        ServiceMethod="GetDropDownContentsBasedOnSelection" ParentControlID="cmbProduct" />
    <div class="controlWrapper">
        <div class="controlLabel">
            <asp:Label ID="lblSerialNumber" runat="server" Text="Serial Number"></asp:Label>
        </div>
        <div class="controlValue1">
            <asp:TextBox ID="txtSerialNumber" runat="server" Text="123456789" Width="120px"></asp:TextBox>
        </div>
        <div class="controlValidator">
            <asp:RequiredFieldValidator ID="serialNumReqFieldValidator" runat="server" 
            ErrorMessage="Please enter serial number" ControlToValidate="txtSerialNumber">*</asp:RequiredFieldValidator>

        </div>
    </div>
    <div class="controlWrapper">
        <div class="controlLabel">
            <asp:Label ID="lblExpiryDate" runat="server" Text="Expiry Date"></asp:Label>
        </div>
        <div class="controlValue1">
            <asp:TextBox ID="txtExpDate" runat="server" Width="120px"></asp:TextBox>
            <ajaxToolkit:CalendarExtender ID="expiryDateCalendarExtender" runat="server" TargetControlID="txtExpDate"
                PopupButtonID="calendarImage" />
        </div>
        <div class="controlValue2">
            <asp:ImageButton ID="calendarImage" runat="Server" ImageUrl="~/Images/Calendar_scheduleHS.png"
                AlternateText="Click to show calendar" />
        </div>
        <div class="controlValidator">
            <asp:RequiredFieldValidator ID="expDateReqFieldValidator" runat="server" ErrorMessage="Please enter a date"  ControlToValidate="txtExpDate">*</asp:RequiredFieldValidator>
            <asp:CustomValidator ID="expDateValidator" runat="server" ControlToValidate="txtExpDate"
                ErrorMessage="Please enter a valid date" OnServerValidate="expDateValidator_ServerValidate">*</asp:CustomValidator>
        </div>
    </div>
    <asp:UpdatePanel ID="CartUpdatePanel" runat="server" UpdateMode="Conditional">
        <ContentTemplate>
            <div class="controlWrapper">
                <div class="controlLabel">
                    <asp:Label ID="lblSelOptions" runat="server" Text="Options In Cart"></asp:Label>
                </div>
                <div class="controlValue1">
                    <asp:ListBox ID="lstBoxSvcOptions" runat="server" Width="120px"></asp:ListBox>
                </div>
            </div>
        </ContentTemplate>
        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="btnAddToCart" EventName="Click" />
            <asp:AsyncPostBackTrigger ControlID="btnClearCart" EventName="Click" />
        </Triggers>
    </asp:UpdatePanel>
    <div class="controlWrapper">
        <div class="controlLabel">
            <asp:Label ID="lblGenKey" runat="server" Text="Generated Key"></asp:Label>
        </div>
        <div class="controlValue1">
            <asp:TextBox ID="txtKeyGenerated" runat="server" Width="120px" ReadOnly="True"></asp:TextBox>
        </div>
    </div>

    <div class="controlWrapper">
        <div class="valSummary">
            <asp:ValidationSummary ID="validationSummary1" runat="server" />
        </div>
    </div>
    <div class="controlWrapper">
        <div class="valSummary">
            <asp:Label ID="lblOprStatus" runat="server"></asp:Label>
        </div>
    </div>
    <div class="controlWrapper">
        <div class="ThreeButton">
            <asp:Button ID="btnGenKey" runat="server" Text="Generate Key"  OnClick="btnGenKey_Click" />
        </div>
        <div class="ThreeButton">
            <asp:Button ID="btnGenKeyFile" runat="server" Text="Generate Key File" OnClick="btnGenKeyFile_Click" />
        </div>
        <div class="ThreeButton">
            <asp:Button ID="btnClearCart" runat="server" Text="Clear Cart" OnClick="btnClearCart_Click" />
        </div>
    </div>
</asp:Content>

有什么解决办法吗？我认为这可能是因为验证器说页面无效。