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Problem with drag and drop in C #

I have a C # .NET 3.5 application that allows me to drag items from a tree and transfer them to a folder as a file. Here is my code

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

This works pretty well, except when interacting with another C # application that accepts files using drag and drop, another C # application has the following handler for DragOver

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

A block is never executed, since e.Data is a __ComObject, not a DataObject. Interestingly, when I drag a file from a folder on top of the second application, it sees it as a DataObject.

How to make a DataObject from the first C # application appear as a DataObject in the second C # application?

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I decided to implement IDataObject using .NET Interop, starting with the IDataObjec t implementation here . Then I defined the structure of DROPFILES

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

and implement code that populates all OLE structures. The function below returns the IDataObject that I use in DoDragDrop:

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; }

With the new code of the second application, he sees DataObject in e.Data , and I can drag and drop the file into any application. In addition, Explorer does not accept files. Am I missing something in my implementation?

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