Question

我有一个简单的嵌套母版层次结构。但是，在运行时，母版页控件（以label1为例）始终为null。

如果Default.aspx更改为直接使用Base.master，则会正确定义母版页控件。

这种行为的原因是什么？

Base.master

<%@ Master Language="C#" CodeFile="Base.master.cs" Inherits="BaseMaster" %>
<!DOCTYPE html>
<html lang="en">
<head runat="server"></head>
<body>
    <form runat="server">
        <asp:Label runat="server" id="label1" Text="Label 1" />
        <asp:ContentPlaceHolder runat="server" ID="MainContent" />
    </form>
</body>
</html>

Base.master.cs

using System;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class BaseMaster : MasterPage
{
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        label1.Text = "Base"; // Causes NullReferenceException
    }
}

Sub.master

<%@ Master Language="C#" CodeFile="Sub.master.cs" Inherits="SubMaster" MasterPageFile="~/Base.master" CodeFileBaseClass="BaseMaster" %>
<asp:Content ID="Content3" ContentPlaceHolderID="MainContent" runat="server">
    <asp:ContentPlaceHolder runat="server" ID="SubMainContent" />
</asp:Content>

Sub.master.cs

using System;
using System.Web.UI;
using System.Web.UI.WebControls;

public partial class SubMaster : BaseMaster
{
    protected override void OnLoad(EventArgs e)
    {
        base.OnLoad(e);
        label1.Text = "Sub"; // Causes NullReferenceException
    }
}

Default.aspx的

<%@ Page Language="C#" CodeFile="Default.aspx.cs" Inherits="DefaultPage" MasterPageFile="~/Sub.master" %>
<asp:Content runat="server" ID="BodyContent" ContentPlaceHolderID="SubMainContent">
    <h3>Default</h3>
</asp:Content>

Default.aspx.cs

using System;
using System.Web;
using System.Web.UI;

public partial class DefaultPage : Page
{
}

使用嵌套母版页时，Control为null

0 个答案: