DragFile.cs

using System;
using System.IO;
using System.Runtime.InteropServices;

namespace NbuExplorer
{
	public class DragFile
	{
		[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 static 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;
		}

	}

}