Add support for IStream & HGlobal drag drops

DragDropViewer/DragDropViewer.csproj

@@ -20,6 +20,7 @@
     <DefineConstants>DEBUG;TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <NoWarn>IDE1006</NoWarn>
   </PropertyGroup>
   <PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">
     <PlatformTarget>AnyCPU</PlatformTarget>
@@ -29,6 +30,7 @@
     <DefineConstants>TRACE</DefineConstants>
     <ErrorReport>prompt</ErrorReport>
     <WarningLevel>4</WarningLevel>
+    <NoWarn>IDE1006</NoWarn>
   </PropertyGroup>
   <ItemGroup>
     <Reference Include="System" />
@@ -44,6 +46,7 @@
     <Reference Include="System.Xml" />
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="ExtensionMethods\ExtensionMethods.cs" />
     <Compile Include="MainForm.cs">
       <SubType>Form</SubType>
     </Compile>

DragDropViewer/ExtensionMethods/ExtensionMethods.cs

@@ -0,0 +1,127 @@
+using System;
+using System.IO;
+using System.Reflection;
+using System.Runtime.InteropServices;
+using System.Runtime.InteropServices.ComTypes;
+using System.Windows.Forms;
+
+namespace DragDropViewer.ExtensionMethods {
+  /// <summary>Helper methods for getting FileContents from DragDrop data.</summary>
+  /// <see cref="!:https://www.codeproject.com/Articles/28209/Outlook-Drag-and-Drop-in-C"/>
+  public static class IDataObjectExtensionMethods {
+    /// <summary>Gets the array of FileNames from the FileGroupDescriptors format.</summary>
+    public static string[] GetFileContentNames(this System.Windows.Forms.IDataObject data) {
+      var names = new string[data.GetFileContentCount()];
+
+      if (names.Length != 0) {
+        var bytes = data.GetFileGroupDescriptor().ToArray();
+        IntPtr fgdPtr = IntPtr.Zero;
+        try {
+          fgdPtr = Marshal.AllocHGlobal(bytes.Length);
+
+          int offset = Marshal.SizeOf(typeof(UInt32));
+          int size = Marshal.SizeOf(typeof(FILEDESCRIPTORW));
+
+          for (int i = 0; i < names.Length; i++) {
+            var fd = (FILEDESCRIPTORW)Marshal.PtrToStructure(fgdPtr + offset + (i * size), typeof(FILEDESCRIPTORW));
+            names[i] = fd.cFileName;
+          }
+
+        } finally {
+          if (fgdPtr != IntPtr.Zero) Marshal.FreeHGlobal(fgdPtr);
+
+        }
+      }
+
+      return names;
+    }
+
+    /// <summary>Gets the number of files available in the FileGroupDescriptor format.</summary>
+    public static int GetFileContentCount(this System.Windows.Forms.IDataObject data) {
+      // File count is stored as an UInt32 in the FileGroupDescriptor format
+      MemoryStream ms = data.GetFileGroupDescriptor();
+      if (ms == null) return 0;
+
+      using (var reader = new BinaryReader(ms)) {
+        return (int)reader.ReadUInt32(); // Assume this won't overflow!
+      }
+    }
+
+    /// <summary>Gets the file content for the specified FileDescriptor index.</summary>
+    /// <param name="index">The index of the file content to retrieve.</param>
+    public static MemoryStream GetFileContent(this System.Windows.Forms.IDataObject data, int index) {
+      // As this is indexed, "FileContent" is most likely null, so the COM IDataObject needs to be used
+      var comData = (System.Runtime.InteropServices.ComTypes.IDataObject)data;
+
+      var formatetc = new FORMATETC() {
+        cfFormat = (short)DataFormats.GetFormat("FileContents").Id,
+        dwAspect = DVASPECT.DVASPECT_CONTENT,
+        lindex = index,
+        ptd = IntPtr.Zero,
+        tymed = TYMED.TYMED_ISTREAM | TYMED.TYMED_HGLOBAL
+      };
+
+      var medium = new STGMEDIUM();
+      comData.GetData(ref formatetc, out medium);
+
+      switch (medium.tymed) {
+        case TYMED.TYMED_HGLOBAL:
+          return data.GetFileContentFromHGlobal(medium);
+
+        case TYMED.TYMED_ISTREAM:
+          return data.GetFileContentFromIStream(medium);
+
+        default:
+          throw new InvalidOperationException($"Cannot get FileContent for {medium.tymed} TYMED.");
+
+      }
+    }
+
+    private static MemoryStream GetFileContentFromHGlobal(this System.Windows.Forms.IDataObject data, STGMEDIUM medium) {
+      var innerDataField = data.GetType().GetField("innerData", BindingFlags.NonPublic | BindingFlags.Instance);
+      var oldData = (System.Windows.Forms.IDataObject)innerDataField.GetValue(data);
+
+      var getDataFromHGLOBLALMethod = oldData.GetType().GetMethod("GetDataFromHGLOBLAL", BindingFlags.NonPublic | BindingFlags.Instance);
+
+      return (MemoryStream)getDataFromHGLOBLALMethod.Invoke(oldData, new object[] { "FileContents", medium.unionmember });
+    }
+
+    private static MemoryStream GetFileContentFromIStream(this System.Windows.Forms.IDataObject data, STGMEDIUM medium) {
+      var iStream = (IStream)Marshal.GetObjectForIUnknown(medium.unionmember);
+      Marshal.Release(medium.unionmember);
+
+      var iStreamStat = new System.Runtime.InteropServices.ComTypes.STATSTG();
+      iStream.Stat(out iStreamStat, 0);
+
+      var content = new byte[(int)iStreamStat.cbSize];
+      iStream.Read(content, content.Length, IntPtr.Zero);
+
+      return new MemoryStream(content);
+    }
+
+    private static MemoryStream GetFileGroupDescriptor(this System.Windows.Forms.IDataObject data) {
+      MemoryStream ms = null;
+      if (data.GetDataPresent("FileGroupDescriptorW")) {
+        ms = (MemoryStream)data.GetData("FileGroupDescriptorW", true);
+      }
+
+      return ms;
+    }
+
+    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
+    private struct FILEDESCRIPTORW {
+      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;
+    }
+  }
+}

DragDropViewer/MainForm.cs

@@ -1,4 +1,5 @@
-using System;
+using DragDropViewer.ExtensionMethods;
+using System;
 using System.Drawing;
 using System.IO;
 using System.Text;
@@ -79,6 +80,33 @@ private void LoadData(IDataObject data) {
         }
       }
 
+      var files = data.GetFileContentNames();
+      if (files.Length != 0) {
+        for (int i = 0; i < files.Length; i++) {
+          object parsedData;
+          using (var ms = data.GetFileContent(i)) {
+            ms.Position = 0;
+            using (var fs = new FileStream("y:\\DragDrop\\foo.jpeg", FileMode.Open, FileAccess.Write)) {
+              ms.WriteTo(fs);
+            }
+            ms.Position = 0;
+
+            try {
+              using (var img = new Bitmap(ms)) {
+                parsedData = new Bitmap(img);
+              }
+            } catch {
+              parsedData = ms.ToArray();
+            }
+          }
+          var item = new DataFormat() {
+            Data = parsedData,
+            Name = $"X-FileContent-{files[i]}"
+          };
+          listFormats.Items.Add(item);
+        }
+      }
+
       listFormats.EndUpdate();
       listFormats.SelectedIndex = -1;
       listFormats.SelectedIndexChanged += listFormats_SelectedIndexChanged;
@@ -120,14 +148,19 @@ private void OnSelectedItemChanged() {
           Lines = (string[])selected.Data
         };
 
-      } else if (selected.Type == typeof(MemoryStream)) {
-        var ms = selected.Data as MemoryStream;
-        ms.Position = 0;
+      } else if ((selected.Type == typeof(MemoryStream)) || (selected.Type == typeof(byte[]))) {
+        byte[] bytes;
+
+        if (selected.Type == typeof(MemoryStream)) {
+          bytes = ((MemoryStream)selected.Data).ToArray();
+        } else {
+          bytes = (byte[])selected.Data;
+        }
 
         string text;
         if (DisplayHex) {
           var sb = new StringBuilder();
-          foreach (byte b in ms.ToArray()) {
+          foreach (byte b in bytes) {
             if (sb.Length != 0) sb.Append(" ");
             sb.Append(b.ToString("x2"));
           }
@@ -144,8 +177,10 @@ private void OnSelectedItemChanged() {
             enc = Encoding.UTF8;
           }
 
-          using (var reader = new StreamReader(ms, enc, true, 1024, true)) {
-            text = reader.ReadToEnd();
+          using (var ms = new MemoryStream(bytes)) {
+            using (var reader = new StreamReader(ms, enc, true, 1024, true)) {
+              text = reader.ReadToEnd();
+            }
           }
         }
 

DragDropViewer/Properties/AssemblyInfo.cs

@@ -32,5 +32,5 @@
 // You can specify all the values or you can default the Build and Revision Numbers
 // by using the '*' as shown below:
 // [assembly: AssemblyVersion("1.0.*")]
-[assembly: AssemblyVersion("1.0.1.0")]
-[assembly: AssemblyFileVersion("1.0.1.0")]
+[assembly: AssemblyVersion("1.1.0.0")]
+[assembly: AssemblyFileVersion("1.1.0.0")]