Question

我目前遇到了一个奇怪的问题。首先，我的代码剪断了：

// This is my base page class
public class MyBasePage
{
    protected override void InitializeCulture()
    {
        base.InitializeCulture();
        MasterPage master = Page.Master; // point1
    }
}

// This is my page
public partial class Default : MyBasePage
{
    protected void Page_Load(object sender, EventArgs e)
    {
         label1.Text = "Test"; // point2
    }
}

通常，point2上的label1不是NULL。但是如果我在InitializeCulture（）事件（point1）中访问母版页，那就是。有人为了解释原因吗？

我想我必须找到另一种解决方法，这对我来说没问题。但我想了解那里发生了什么。

Answer 1

这是因为主页和主题在初始化期间应用于页面，并且在此之前调用InitializeCulture，因此它返回null。

Answer 2

我用ILSpy分析了这种行为。问题是，母版页未在InitializeCulture事件中初始化，如果被访问，它将被初始化 - 但显然不正确。

结论：永远不要从InitializeCulture事件访问母版页 - 它会搞乱页面初始化过程。

这里，仅供参考，初始化母版页的.NET代码：

internal static MasterPage CreateMaster(TemplateControl owner, HttpContext context, VirtualPath masterPageFile, IDictionary contentTemplateCollection)
{
    MasterPage masterPage = null;
    if (masterPageFile == null)
    {
        if (contentTemplateCollection != null && contentTemplateCollection.Count > 0)
        {
            throw new HttpException(SR.GetString("Content_only_allowed_in_content_page"));
        }
        return null;
    }
    else
    {
        VirtualPath virtualPath = VirtualPathProvider.CombineVirtualPathsInternal(owner.TemplateControlVirtualPath, masterPageFile);
        ITypedWebObjectFactory typedWebObjectFactory = (ITypedWebObjectFactory)BuildManager.GetVPathBuildResult(context, virtualPath);
        if (!typeof(MasterPage).IsAssignableFrom(typedWebObjectFactory.InstantiatedType))
        {
            throw new HttpException(SR.GetString("Invalid_master_base", new object[]
            {
                masterPageFile
            }));
        }
        masterPage = (MasterPage)typedWebObjectFactory.CreateInstance();
        masterPage.TemplateControlVirtualPath = virtualPath;
        if (owner.HasControls())
        {
            foreach (Control control in owner.Controls)
            {
                LiteralControl literalControl = control as LiteralControl;
                if (literalControl == null || Util.FirstNonWhiteSpaceIndex(literalControl.Text) >= 0)
                {
                    throw new HttpException(SR.GetString("Content_allowed_in_top_level_only"));
                }
            }
            owner.Controls.Clear();
        }
        if (owner.Controls.IsReadOnly)
        {
            throw new HttpException(SR.GetString("MasterPage_Cannot_ApplyTo_ReadOnly_Collection"));
        }
        if (contentTemplateCollection != null)
        {
            foreach (string text in contentTemplateCollection.Keys)
            {
                if (!masterPage.ContentPlaceHolders.Contains(text.ToLower(CultureInfo.InvariantCulture)))
                {
                    throw new HttpException(SR.GetString("MasterPage_doesnt_have_contentplaceholder", new object[]
                    {
                        text,
                        masterPageFile
                    }));
                }
            }
            masterPage._contentTemplates = contentTemplateCollection;
        }
        masterPage._ownerControl = owner;
        masterPage.InitializeAsUserControl(owner.Page);
        owner.Controls.Add(masterPage);
        return masterPage;
    }
}

System.Web.UI.Page覆盖InitializeCulture并访问MasterPage

2 个答案: