c# - 如何使用文件组描述符将文件拖到资源管理器 C#

Question

我想将列表框的一个元素拖放到资源管理器中。当拖放开始时，我需要按需准备文件并将其保存到内存流中。你能给我提供一个例子，说明如何使用 FileGroupDescriptor 数据结构来做到这一点吗？谢谢。安德里亚

Answer 1

您可以在此处找到有关如何执行此操作的示例 Transferring Virtual Files to Windows Explorer in C# ;这里还有一些关于该主题的好信息:Outlook Drag and Drop in C#

简而言之，您要做的是使用 FILEDESCRIPTOR(您可以在 pinvoke.net 上找到它的声明详细信息)结构初始化 DataObject 以获取传输的文件及其内容。下面是一个关于如何将 1 文件从 winforms ListBox 传输到资源管理器的示例。

列表框的鼠标按下事件处理程序:

private void listBox1_MouseDown(object sender, MouseEventArgs e)
{
    DataObject dataObject = new DataObject();
    DragFileInfo filesInfo = new DragFileInfo("d:\\test.txt");

    using (MemoryStream infoStream = GetFileDescriptor(filesInfo),
                        contentStream = GetFileContents(filesInfo))
    {
        dataObject.SetData(CFSTR_FILEDESCRIPTORW, infoStream);
        dataObject.SetData(CFSTR_FILECONTENTS, contentStream);
        dataObject.SetData(CFSTR_PERFORMEDDROPEFFECT, null);

        DoDragDrop(dataObject, DragDropEffects.All);
    }
}

初始化数据对象所需的代码:

[StructLayout(LayoutKind.Sequential, CharSet=CharSet.Auto)]
struct FILEDESCRIPTOR
{
    public UInt32 dwFlags;
    public Guid clsid;
    public System.Drawing.Size sizel;
    public System.Drawing.Point pointl;
    public UInt32 dwFileAttributes;
    public System.Runtime.InteropServices.ComTypes.FILETIME ftCreationTime;
    public System.Runtime.InteropServices.ComTypes.FILETIME ftLastAccessTime;
    public System.Runtime.InteropServices.ComTypes.FILETIME ftLastWriteTime;
    public UInt32 nFileSizeHigh;
    public UInt32 nFileSizeLow;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst=260)]
    public String cFileName;
}

public const string CFSTR_PREFERREDDROPEFFECT = "Preferred DropEffect";
public const string CFSTR_PERFORMEDDROPEFFECT = "Performed DropEffect";
public const string CFSTR_FILEDESCRIPTORW = "FileGroupDescriptorW";
public const string CFSTR_FILECONTENTS = "FileContents";

public const Int32 FD_WRITESTIME = 0x00000020;
public const Int32 FD_FILESIZE = 0x00000040;
public const Int32 FD_PROGRESSUI = 0x00004000;

public struct DragFileInfo
{
    public string FileName;
    public string SourceFileName;
    public DateTime WriteTime;
    public Int64 FileSize;

    public DragFileInfo(string fileName)
    {
        FileName = Path.GetFileName(fileName);
        SourceFileName = fileName;
        WriteTime = DateTime.Now;
        FileSize = (new FileInfo(fileName)).Length;
    }
}

private MemoryStream GetFileDescriptor(DragFileInfo fileInfo)
{
    MemoryStream stream = new MemoryStream();
    stream.Write(BitConverter.GetBytes(1), 0, sizeof(UInt32));

    FILEDESCRIPTOR fileDescriptor = new FILEDESCRIPTOR();

    fileDescriptor.cFileName = fileInfo.FileName;
    Int64 fileWriteTimeUtc = fileInfo.WriteTime.ToFileTimeUtc();
    fileDescriptor.ftLastWriteTime.dwHighDateTime = (Int32)(fileWriteTimeUtc >> 32);
    fileDescriptor.ftLastWriteTime.dwLowDateTime = (Int32)(fileWriteTimeUtc & 0xFFFFFFFF);
    fileDescriptor.nFileSizeHigh = (UInt32)(fileInfo.FileSize >> 32);
    fileDescriptor.nFileSizeLow = (UInt32)(fileInfo.FileSize & 0xFFFFFFFF);
    fileDescriptor.dwFlags = FD_WRITESTIME | FD_FILESIZE | FD_PROGRESSUI;

    Int32   fileDescriptorSize = Marshal.SizeOf(fileDescriptor);
    IntPtr  fileDescriptorPointer = Marshal.AllocHGlobal(fileDescriptorSize);
    Byte[]  fileDescriptorByteArray = new Byte[fileDescriptorSize];

    try
    {
        Marshal.StructureToPtr(fileDescriptor, fileDescriptorPointer, true);
        Marshal.Copy(fileDescriptorPointer, fileDescriptorByteArray, 0, fileDescriptorSize);
    }
    finally
    {
        Marshal.FreeHGlobal(fileDescriptorPointer);
    }
    stream.Write(fileDescriptorByteArray, 0, fileDescriptorByteArray.Length);
    return stream;
}

private MemoryStream GetFileContents(DragFileInfo fileInfo)
{
    MemoryStream stream  = new MemoryStream();            
    using (BinaryReader reader = new BinaryReader(File.OpenRead(fileInfo.SourceFileName)))
    {
        Byte[] buffer = new Byte[fileInfo.FileSize];
        reader.Read(buffer, 0, (Int32)fileInfo.FileSize);
        if (buffer.Length == 0) buffer = new Byte[1];
        stream.Write(buffer, 0, buffer.Length);
    }
    return stream;
}

希望这会给你一个关于如何继续的想法，问候