C#拖放问题

2023年7月24日 158次阅读

我有一个C#.NET 3.5应用程序,它允许从树中拖动项目并将它们作为文件放到文件夹中.这是我的代码

String absolutePathToFile=...get absolute path
DataObject dataObject = new DataObject();
StringCollection paths = new StringCollection();
paths.Add(absolutePathToFile);
dataObject.SetFileDropList(paths);
DoDragDrop(dataObject, DragDropEffects.Copy);

这很有效,除非与另一个通过拖放接受文件的C#应用​​程序交互时,另一个C#应用程序具有以下DragOver处理程序

if ((e.Data is DataObject) && (e.Data as DataObject).ContainsFileDropList())
{
    e.Effect = DragDropEffects.Copy;
}

由于e.Data是__ComObject而不是DataObject,因此永远不会执行该块.有趣的是,当我从第二个应用程序的文件夹中拖动文件时,它将其视为DataObject.

如何从第一个C#应用程序使DataObject在第二个C#应用程序中显示为DataObject？

最佳答案 我决定使用.NET Interop从
here的IDataObject实现开始实现IDataObject.然后我定义了DROPFILES结构

[StructLayoutAttribute(LayoutKind.Sequential)]
internal struct _DROPFILES
{
    public Int32 pFiles;
    public Int32 X;
    public Int32 Y;
    public bool fNC;
    public bool fWide;
}

并实现填充所有OLE结构的代码.下面的函数返回我在DoDragDrop中使用的IDataObject：

DoDragDrop(GetDataObject(new String [] {file name}),DragDropEffects.Copy);

DataObject2 GetDataObject(String[] strFiles)
{
    byte[] bData;
    _DROPFILES df = new _DROPFILES();
    int intChar, intFile, intDataLen, intPos;
    IntPtr ipGlobal = IntPtr.Zero;

    // Calculate total data length
    intDataLen = 0;
    for (intFile = 0; intFile <= strFiles.GetUpperBound(0);intFile++)
    {
        intDataLen += strFiles[intFile].Length + 1;
    }
    // Terminating double zero
    intDataLen++;

    bData = new Byte[intDataLen];
    intPos = 0;

    // Build null terminated list of files
    for (intFile = 0; intFile <= strFiles.GetUpperBound(0); intFile++)
    {
        for (intChar = 0; intChar < strFiles[intFile].Length;intChar++)
        {
            bData[intPos++] = (byte)strFiles[intFile][intChar];
        }
        bData[intPos++] = 0;
    }
    // Terminating double zero
    bData[intPos++] = 0;

    // Allocate and get pointer to global memory
    int intTotalLen = Marshal.SizeOf(df) + intDataLen;
    ipGlobal = Marshal.AllocHGlobal(intTotalLen);

    if (ipGlobal == IntPtr.Zero)
    {
        return null;
    }

    // Build DROPFILES structure in global memory.
    df.pFiles = Marshal.SizeOf(df);
    df.fWide = false;
    Marshal.StructureToPtr(df, ipGlobal, true);
    IntPtr ipNew = new IntPtr(ipGlobal.ToInt32() + Marshal.SizeOf(df));
    Marshal.Copy(bData, 0, ipNew, intDataLen);

    short CF_HDROP = 15;
    System.Runtime.InteropServices.ComTypes.FORMATETC formatEtc;
    System.Runtime.InteropServices.ComTypes.STGMEDIUM stgMedium;

    formatEtc = new System.Runtime.InteropServices.ComTypes.FORMATETC();
    formatEtc.cfFormat = CF_HDROP;
    formatEtc.dwAspect = System.Runtime.InteropServices.ComTypes.DVASPECT.DVASPECT_CONTENT;
    formatEtc.lindex = -1;
    formatEtc.tymed = System.Runtime.InteropServices.ComTypes.TYMED.TYMED_HGLOBAL;

    stgMedium = new System.Runtime.InteropServices.ComTypes.STGMEDIUM();
    stgMedium.unionmember = ipGlobal;
    stgMedium.tymed = System.Runtime.InteropServices.ComTypes.TYMED.TYMED_HGLOBAL;
    DataObject2 dobj = new DataObject2();
    dobj.SetData(ref formatEtc, ref stgMedium, false);
    return dobj;

}

使用新代码第二个应用程序在e.Data中看到DataObject,我可以将文件拖放到任何应用程序.除了现在Explorer不接受文件.我的实施中是否会遗漏一些内容？

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