asp.net – UpdatePanel没有名为’TextBox’的公共属性.

见下面的代码：

<asp:ScriptManager runat="server" ID="ScriptManager" />
    <asp:UpdatePanel runat="server" ID="brandAddingContainer" Visible="false">
        <ContentTemplate>
            <asp:LinkButton runat="server" ID="brandAddingPrompt">
                <img src="/images/add.gif" alt="Add New Brand" onclick="addNewBrand_clicked"/> Add New Brand
            </asp:LinkButton>

            <asp:Panel ID="sendNewBrand" runat="server">
                <asp:TextBox runat="server" ID="newBrandName"></asp:TextBox>
                <asp:Button runat="server" ID="sendBrandName" Text="Add Brand" OnClick="sendNewBrand_clicked" />
                <asp:Label runat="server" ID="insertionFeedback" Visible="false" />
            </asp:Panel>
        </ContentTemplate>

        <Triggers>
            <asp:AsyncPostBackTrigger ControlID="brandAddingPrompt" EventName="Click" />
        </Triggers>
    </asp:UpdatePanel>