CDN_SELCHANGE通知消息由FileOpenDialog为32位构建生成而不是为64位生成生成

Question

我从微软编写的网站下载"Extensible“(使用P/Invoke的C#)，演示如何将Windows控件放置在一个常见的文件对话框中。(例如:添加预览功能)。此项目具有测试客户端代码，即打开对话框，一旦单击图片，就可以在对话框的右侧预览图片。测试客户端代码在32位构建中运行良好，但在64位构建中不工作。

经过一些调试后，我发现这是因为在64位构建中，CDN_SELCHANGE通知消息来自

    [DllImport("ComDlg32.dll", CharSet = CharSet.Unicode)]
    internal static extern bool GetOpenFileName( ref OpenFileName ofn );

在c#代码中无法识别或无法正确处理。

// WM_NOTIFY - we're only interested in the CDN_SELCHANGE notification message
// we grab the currently-selected filename and fire our event
case WindowMessage.Notify:
{
    IntPtr ipNotify = new IntPtr( lParam );
    OfNotify ofNot = (OfNotify)Marshal.PtrToStructure( ipNotify, typeof(OfNotify) );
    UInt16 code = ofNot.hdr.code;
    if( code == CommonDlgNotification.SelChange )
    {
       // This is the first time we can rely on the presence of the content panel
       // Resize the content and user-supplied panels to fit nicely
       FindAndResizePanels( hWnd );

       // get the newly-selected path
       IntPtr hWndParent = NativeMethods.GetParent( hWnd );
       StringBuilder pathBuffer = new StringBuilder(_MAX_PATH);
       UInt32 ret = NativeMethods.SendMessage( hWndParent, CommonDlgMessage.GetFilePath, _MAX_PATH, pathBuffer );
       string path = pathBuffer.ToString();

       // copy the string into the path buffer
       UnicodeEncoding ue = new UnicodeEncoding();
       byte[] pathBytes = ue.GetBytes( path );
       Marshal.Copy( pathBytes, 0, _fileNameBuffer, pathBytes.Length );

       // fire selection-changed event
       if( SelectionChanged != null ) SelectionChanged( path );
     }
     return IntPtr.Zero;
}

即使我在OpenFileDialog中选择了不同的文件，ofNot.hdr.code始终是0，因此，应用程序在if( code == CommonDlgNotification.SelChange )之后永远不会遇到代码块。有人能让这个测试样本在64位构建中工作吗？提前感谢！

示例代码下载链接：ExtensibleDialogsSource.msi

Answer 1

感谢所有的回复，我想出了解决办法。当结构定义应用于64位应用程序时，它的定义是错误的。在NativeMethods.cs (由微软编写，可能不针对64位应用程序)中，它定义了

/// <summary>
/// Part of the notification messages sent by the common dialogs
/// </summary>
[StructLayout(LayoutKind.Explicit)]
internal struct NMHDR
{
    [FieldOffset(0)]    public IntPtr   hWndFrom;
    [FieldOffset(4)]    public UInt16   idFrom;
    [FieldOffset(8)]    public UInt16   code;
};

/// <summary>
/// Part of the notification messages sent by the common dialogs
/// </summary>
[StructLayout(LayoutKind.Explicit)]
internal struct OfNotify
{
    [FieldOffset(0)]    public NMHDR    hdr;
    [FieldOffset(12)]   public IntPtr   ipOfn;
    [FieldOffset(16)]   public IntPtr   ipFile;
};

由于IntPtr的大小从4字节更改为8字节，所以我们需要IntPtr重新定义结构。

[StructLayout(LayoutKind.Explicit)]
internal struct NMHDR
{
    [FieldOffset(0)]
    public IntPtr hWndFrom;
    [FieldOffset(8)]
    public IntPtr idFrom;
    [FieldOffset(16)]
    public UInt16 code;
};

/// <summary>
/// Part of the notification messages sent by the common dialogs
/// </summary>
[StructLayout(LayoutKind.Explicit)]
internal struct OfNotify
{
    [FieldOffset(0)]
    public NMHDR hdr;
    [FieldOffset(20)]
    public IntPtr ipOfn;
    [FieldOffset(28)]
    public IntPtr ipFile;
};

现在它适用于64位应用程序。

在我看来，如果可能的话，我们最好使用.Net库，这样可以使生活更轻松。

Answer 2

NMHDR idFrom不是IntPtr，而是MSDN2005中的UINT。后来被记录为UINT_PTR..。