New Post: This is not working on my preview host windows form

using System;using System.Windows.Forms;using System.Windows.Forms.Design;using System.Runtime.InteropServices;using System.Runtime.InteropServices.ComTypes;using Microsoft.Win32;using System.IO;using System.ComponentModel;using System.Drawing;using System.Drawing.Design;publicclass PreviewHandlerHost : Control {internalconststring GUID_ISHELLITEM = "43826d1e-e718-42ee-bc55-a1e261c37bfe";privateobject mCurrentPreviewHandler;private Guid mCurrentPreviewHandlerGUID;private Stream mCurrentPreviewHandlerStream;privatestring mErrorMessage;privatestring ErrorMessage {get { return mErrorMessage; }set {
			mErrorMessage = value;
			Invalidate();	// repaint the control
		}
	}///<summary>/// Gets or sets the background colour of this PreviewHandlerHost.///</summary>
	[DefaultValue("White")]publicoverride System.Drawing.Color BackColor {get {returnbase.BackColor;
		}set {base.BackColor = value;
		}
	}///<summary>/// Initialialises a new instance of the PreviewHandlerHost class.///</summary>public PreviewHandlerHost() : base() {
		mCurrentPreviewHandlerGUID = Guid.Empty;
		BackColor = Color.White;
		Size = new Size(320, 240);// display default error message (no file)
		ErrorMessage = "No file loaded.";// enable transparency
		SetStyle(ControlStyles.SupportsTransparentBackColor, true);
		SetStyle(ControlStyles.UserPaint, true);
	}///<summary>/// Releases the unmanaged resources used by the PreviewHandlerHost and optionally releases the managed resources.///</summary>///<param name="disposing"></param>protectedoverridevoid Dispose(bool disposing) {
		UnloadPreviewHandler();if (mCurrentPreviewHandler != null) {
			Marshal.FinalReleaseComObject(mCurrentPreviewHandler);
			mCurrentPreviewHandler = null;
			GC.Collect();
		}base.Dispose(disposing);
	}private Guid GetPreviewHandlerGUID(string filename) {// open the registry key corresponding to the file extension
		RegistryKey ext = Registry.ClassesRoot.OpenSubKey(Path.GetExtension(filename));if (ext != null) {// open the key that indicates the GUID of the preview handler type
			RegistryKey test = ext.OpenSubKey("shellex\\{8895b1c6-b41f-4c1c-a562-0d564250836f}");if (test != null) returnnew Guid(Convert.ToString(test.GetValue(null)));// sometimes preview handlers are declared on key for the classstring className = Convert.ToString(ext.GetValue(null));if (className != null) {
				test = Registry.ClassesRoot.OpenSubKey(className + "\\shellex\\{8895b1c6-b41f-4c1c-a562-0d564250836f}");if (test != null) returnnew Guid(Convert.ToString(test.GetValue(null)));
			}
		}return Guid.Empty;
	}///<summary>/// Paints the error message text on the PreviewHandlerHost control.///</summary>///<param name="e"></param>protectedoverridevoid OnPaint(PaintEventArgs e) {base.OnPaint(e);if (mErrorMessage != String.Empty) {// paint the error message
			TextRenderer.DrawText(
				e.Graphics, 
				mErrorMessage, 
				Font, 
				ClientRectangle, 
				ForeColor, 
				TextFormatFlags.HorizontalCenter | TextFormatFlags.VerticalCenter | TextFormatFlags.EndEllipsis
			);
		}
	}///<summary>/// Resizes the hosted preview handler when this PreviewHandlerHost is resized.///</summary>///<param name="e"></param>protectedoverridevoid OnResize(EventArgs e) {base.OnResize(e);if (mCurrentPreviewHandler is IPreviewHandler) {// update the preview handler's bounds to match the control's
			Rectangle r = ClientRectangle;
			((IPreviewHandler)mCurrentPreviewHandler).SetWindow(Handle, ref r);
		}
	}///<summary>/// Opens the specified file using the appropriate preview handler and displays the result in this PreviewHandlerHost.///</summary>///<param name="filename"></param>///<returns></returns>publicbool Open(string filename) {
		UnloadPreviewHandler();if (String.IsNullOrEmpty(filename)) {
			ErrorMessage = "No file loaded.";returnfalse;
		}// try to get GUID for the preview handler
		Guid guid = GetPreviewHandlerGUID(filename);
		ErrorMessage = "";if (guid != Guid.Empty) {try {if (guid != mCurrentPreviewHandlerGUID) {
					mCurrentPreviewHandlerGUID = guid;// need to instantiate a different COM type (file format has changed)if (mCurrentPreviewHandler != null) Marshal.FinalReleaseComObject(mCurrentPreviewHandler);					// use reflection to instantiate the preview handler type
					Type comType = Type.GetTypeFromCLSID(mCurrentPreviewHandlerGUID);
					mCurrentPreviewHandler = Activator.CreateInstance(comType);
				}if (mCurrentPreviewHandler is IInitializeWithFile) {// some handlers accept a filename
					((IInitializeWithFile)mCurrentPreviewHandler).Initialize(filename, 0);
				}elseif (mCurrentPreviewHandler is IInitializeWithStream) {if (File.Exists(filename)) {// other handlers want an IStream (in this case, a file stream)
						mCurrentPreviewHandlerStream = File.Open(filename, FileMode.Open);
						StreamWrapper stream = new StreamWrapper(mCurrentPreviewHandlerStream);
						((IInitializeWithStream)mCurrentPreviewHandler).Initialize(stream, 0);
					}else {
						ErrorMessage = "File not found.";
					}
				}elseif (mCurrentPreviewHandler is IInitializeWithItem) {// a third category exists, must be initialised with a shell item
					IShellItem shellItem;
					SHCreateItemFromParsingName(filename, IntPtr.Zero, new Guid(GUID_ISHELLITEM), out shellItem);
					((IInitializeWithItem)mCurrentPreviewHandler).Initialize(shellItem, 0);
				}if (mCurrentPreviewHandler is IPreviewHandler) {// bind the preview handler to the control's bounds and preview the content
					Rectangle r = ClientRectangle;
					((IPreviewHandler)mCurrentPreviewHandler).SetWindow(Handle, ref r);
					((IPreviewHandler)mCurrentPreviewHandler).DoPreview();returntrue;
				}
			}catch (Exception ex) {
				ErrorMessage = "Preview could not be generated.\n"+ ex.Message;
			}
		}else {
			ErrorMessage = "No preview available.";
		}returnfalse;
	}///<summary>/// Opens the specified stream using the preview handler COM type with the provided GUID and displays the result in this PreviewHandlerHost.///</summary>///<param name="stream"></param>///<param name="previewHandler"></param>///<returns></returns>publicbool Open(Stream stream, Guid previewHandler) {
		UnloadPreviewHandler();if (stream == null) {
			ErrorMessage = "No file loaded.";returnfalse;
		}

		ErrorMessage = "";if (previewHandler != Guid.Empty) {try {if (previewHandler != mCurrentPreviewHandlerGUID) {
					mCurrentPreviewHandlerGUID = previewHandler;// need to instantiate a different COM type (file format has changed)if (mCurrentPreviewHandler != null) Marshal.FinalReleaseComObject(mCurrentPreviewHandler);// use reflection to instantiate the preview handler type
					Type comType = Type.GetTypeFromCLSID(mCurrentPreviewHandlerGUID);
					mCurrentPreviewHandler = Activator.CreateInstance(comType);
				}if (mCurrentPreviewHandler is IInitializeWithStream) {// must wrap the stream to provide compatibility with IStream
					mCurrentPreviewHandlerStream = stream;
					StreamWrapper wrapped = new StreamWrapper(mCurrentPreviewHandlerStream);
					((IInitializeWithStream)mCurrentPreviewHandler).Initialize(wrapped, 0);
				}if (mCurrentPreviewHandler is IPreviewHandler) {// bind the preview handler to the control's bounds and preview the content
					Rectangle r = ClientRectangle;
					((IPreviewHandler)mCurrentPreviewHandler).SetWindow(Handle, ref r);
					((IPreviewHandler)mCurrentPreviewHandler).DoPreview();returntrue;
				}
			}catch (Exception ex) {
				ErrorMessage = "Preview could not be generated.\n"+ ex.Message;
			}
		}else {
			ErrorMessage = "No preview available.";
		}returnfalse;
	}///<summary>/// Unloads the preview handler hosted in this PreviewHandlerHost and closes the file stream.///</summary>publicvoid UnloadPreviewHandler() {if (mCurrentPreviewHandler is IPreviewHandler) {// explicitly unload the content
			((IPreviewHandler)mCurrentPreviewHandler).Unload();
		}if (mCurrentPreviewHandlerStream != null) {
			mCurrentPreviewHandlerStream.Close();
			mCurrentPreviewHandlerStream = null;
		}
	}#region P/Invoke

	[DllImport("shell32.dll", CharSet = CharSet.Unicode, PreserveSig = false)]staticexternvoid SHCreateItemFromParsingName(
		[In][MarshalAs(UnmanagedType.LPWStr)] string pszPath,
		[In] IntPtr pbc, [In][MarshalAs(UnmanagedType.LPStruct)] Guid riid,
		[Out][MarshalAs(UnmanagedType.Interface, IidParameterIndex = 2)] out IShellItem ppv
	);#endregion
}#region COM Interop

[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("8895b1c6-b41f-4c1c-a562-0d564250836f")]internalinterface IPreviewHandler {void SetWindow(IntPtr hwnd, ref Rectangle rect);void SetRect(ref Rectangle rect);void DoPreview();void Unload();void SetFocus();void QueryFocus(out IntPtr phwnd);
	[PreserveSig]uint TranslateAccelerator(ref Message pmsg);
}

[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("b7d14566-0509-4cce-a71f-0a554233bd9b")]internalinterface IInitializeWithFile {void Initialize([MarshalAs(UnmanagedType.LPWStr)] string pszFilePath, uint grfMode);
}

[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("b824b49d-22ac-4161-ac8a-9916e8fa3f7f")]internalinterface IInitializeWithStream {void Initialize(IStream pstream, uint grfMode);
}

[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid("7F73BE3F-FB79-493C-A6C7-7EE14E245841")]interface IInitializeWithItem {void Initialize(IShellItem psi, uint grfMode);
}

[ComImport, InterfaceType(ComInterfaceType.InterfaceIsIUnknown), Guid(PreviewHandlerHost.GUID_ISHELLITEM)]
interface IShellItem {void BindToHandler(IntPtr pbc, [MarshalAs(UnmanagedType.LPStruct)]Guid bhid, [MarshalAs(UnmanagedType.LPStruct)]Guid riid, out IntPtr ppv);void GetParent(out IShellItem ppsi);void GetDisplayName(uint sigdnName, out IntPtr ppszName);void GetAttributes(uint sfgaoMask, outuint psfgaoAttribs);void Compare(IShellItem psi, uint hint, outint piOrder);
};///<summary>/// Provides a bare-bones implementation of System.Runtime.InteropServices.IStream that wraps an System.IO.Stream.///</summary>
[ClassInterface(ClassInterfaceType.AutoDispatch)]internalclass StreamWrapper : IStream {private System.IO.Stream mInner;///<summary>/// Initialises a new instance of the StreamWrapper class, using the specified System.IO.Stream.///</summary>///<param name="inner"></param>public StreamWrapper(System.IO.Stream inner) {
		mInner = inner;
	}///<summary>/// This operation is not supported.///</summary>///<param name="ppstm"></param>publicvoid Clone(out IStream ppstm) {thrownew NotSupportedException();
	}///<summary>/// This operation is not supported.///</summary>///<param name="grfCommitFlags"></param>publicvoid Commit(int grfCommitFlags) {thrownew NotSupportedException();
	}///<summary>/// This operation is not supported.///</summary>///<param name="pstm"></param>///<param name="cb"></param>///<param name="pcbRead"></param>///<param name="pcbWritten"></param>publicvoid CopyTo(IStream pstm, long cb, IntPtr pcbRead, IntPtr pcbWritten) {thrownew NotSupportedException();
	}///<summary>/// This operation is not supported.///</summary>///<param name="libOffset"></param>///<param name="cb"></param>///<param name="dwLockType"></param>publicvoid LockRegion(long libOffset, long cb, int dwLockType) {thrownew NotSupportedException();
	}///<summary>/// Reads a sequence of bytes from the underlying System.IO.Stream.///</summary>///<param name="pv"></param>///<param name="cb"></param>///<param name="pcbRead"></param>publicvoid Read(byte[] pv, int cb, IntPtr pcbRead) {long bytesRead = mInner.Read(pv, 0, cb);if (pcbRead != IntPtr.Zero) Marshal.WriteInt64(pcbRead, bytesRead);
	}///<summary>/// This operation is not supported.///</summary>publicvoid Revert() {thrownew NotSupportedException();
	}///<summary>/// Advances the stream to the specified position.///</summary>///<param name="dlibMove"></param>///<param name="dwOrigin"></param>///<param name="plibNewPosition"></param>publicvoid Seek(long dlibMove, int dwOrigin, IntPtr plibNewPosition) {long pos = mInner.Seek(dlibMove, (System.IO.SeekOrigin)dwOrigin);if (plibNewPosition != IntPtr.Zero) Marshal.WriteInt64(plibNewPosition, pos); 
	}///<summary>/// This operation is not supported.///</summary>///<param name="libNewSize"></param>publicvoid SetSize(long libNewSize) {thrownew NotSupportedException();
	}///<summary>/// Returns details about the stream, including its length, type and name.///</summary>///<param name="pstatstg"></param>///<param name="grfStatFlag"></param>publicvoid Stat(out System.Runtime.InteropServices.ComTypes.STATSTG pstatstg, int grfStatFlag) {
		pstatstg = new System.Runtime.InteropServices.ComTypes.STATSTG();
		pstatstg.cbSize = mInner.Length;
		pstatstg.type = 2; // stream type
		pstatstg.pwcsName = (mInner is FileStream) ? ((FileStream)mInner).Name : String.Empty;
	}///<summary>/// This operation is not supported.///</summary>///<param name="libOffset"></param>///<param name="cb"></param>///<param name="dwLockType"></param>publicvoid UnlockRegion(long libOffset, long cb, int dwLockType) {thrownew NotSupportedException();
	}///<summary>/// Writes a sequence of bytes to the underlying System.IO.Stream.///</summary>///<param name="pv"></param>///<param name="cb"></param>///<param name="pcbWritten"></param>publicvoid Write(byte[] pv, int cb, IntPtr pcbWritten) {
		mInner.Write(pv, 0, cb);if (pcbWritten != IntPtr.Zero) Marshal.WriteInt64(pcbWritten, (Int64)cb);
	}
}#endregion