IActiveDesktop in Csharp

private ActiveDesktop dummy;
private IActiveDesktop IActive;
private void button1_Click(object sender, System.EventArgs e)
{
	dummy = new ActiveDesktop();
	IActive = (IActiveDesktop)dummy; // cast an instance of the IActiveDesktop from the ActiveDesktop Class. 

	System.Text.StringBuilder sb=new System.Text.StringBuilder(256);
	IActive.GetWallpaper(sb , sb.Capacity,0);
	MessageBox.Show(sb.ToString());
}

private void button2_Click(object sender, System.EventArgs e)
{
	IActive.SetWallpaper(textBox2.Text,0);
	IActive.ApplyChanges(_win32.AD_APPLY_FORCE | _win32.AD_APPLY_SAVE | _win32.AD_APPLY_REFRESH);
}

	`#region ActiveDesktop class`
	`[ComImport(),Guid("75048700-EF1F-11D0-9888-006097DEACF9")] public class ActiveDesktop { // dummy to enable access to the IActiveDesktop } #endregion`

#region IActiveDesktop interface

[ComImport(),Guid("F490EB00-1240-11D1-9888-006097DEACF9"),InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
public interface IActiveDesktop
{
	IntPtr  ApplyChanges(          int dwFlags
		); //HRESULT ApplyChanges(DWORD dwFlags);
	
	IntPtr  GetWallpaper([MarshalAs(UnmanagedType.LPWStr)]System.Text.StringBuilder pwszWallpaper,
	int cchWallpaper,
	int dwReserved
	); // HRESULT GetWallpaper(LPWSTR pwszWallpaper,UINT cchWallpaper,DWORD dwReserved);

	IntPtr SetWallpaper([MarshalAs(UnmanagedType.LPWStr)]string pwszWallpaper,
		int dwReserved
		); // HRESULT SetWallpaper(LPCWSTR pwszWallpaper,DWORD dwReserved);
	
	IntPtr  GetWallpaperOptions(ref          _win32._tagWALLPAPEROPT pwpo,
		int dwReserved
		); // HRESULT GetWallpaperOptions(LPWALLPAPEROPT pwpo,DWORD dwReserved);

	IntPtr SetWallpaperOptions([In] ref          _win32._tagWALLPAPEROPT pwpo,
		int dwReserved
		); // HRESULT SetWallpaperOptions(LPCWALLPAPEROPT pwpo,DWORD dwReserved);

	IntPtr  GetPattern([MarshalAs(UnmanagedType.LPWStr)]System.Text.StringBuilder pwszPattern,
		int cchPattern,
		int dwReserved
		); //HRESULT GetPattern(LPWSTR pwszPattern,UINT cchPattern,DWORD dwReserved);

	IntPtr SetPattern([MarshalAs(UnmanagedType.LPWStr)]string pwszPattern,
		int dwReserved
		); // HRESULT SetPattern(LPCWSTR pwszPattern,DWORD dwReserved);

	IntPtr  GetDesktopItemOptions(ref          _win32._tagCOMPONENTSOPT pco,
		int dwReserved
		); // HRESULT GetDesktopItemOptions(LPCOMPONENTSOPT pco,DWORD dwReserved);

	IntPtr  SetDesktopItemOptions([In]ref           _win32._tagCOMPONENTSOPT pcomp,
		int dwReserved
		); // HRESULT SetDesktopItemOptions(LPCCOMPONENTSOPT pcomp,DWORD dwReserved);

	IntPtr  AddDesktopItem([In]ref           _win32._tagCOMPONENT pcomp,
		int dwReserved
		); // HRESULT AddDesktopItem(LPCOMPONENT pcomp,DWORD dwReserved);

	IntPtr  AddDesktopItemWithUI(          IntPtr hwnd,
		[In]ref _win32._tagCOMPONENT pcomp,
		int dwFlags
		); // HRESULT AddDesktopItemWithUI(HWND hwnd,LPCOMPONENT pcomp,DWORD dwFlags);

	IntPtr  ModifyDesktopItem([In]ref           _win32._tagCOMPONENT pcomp,
		int dwFlags
		); // HRESULT ModifyDesktopItem(LPCCOMPONENT pcomp,DWORD dwFlags);
	
	IntPtr  RemoveDesktopItem([In]ref           _win32._tagCOMPONENT pcomp,
		int dwReserved
		); // HRESULT RemoveDesktopItem(LPCCOMPONENT pcomp,DWORD dwReserved);

	IntPtr  GetDesktopItemCount(out          int lpiCount,
		int dwReserved
		); // HRESULT GetDesktopItemCount(LPINT lpiCount,DWORD dwReserved);

	IntPtr  GetDesktopItem(          int nComponent,
		ref _win32._tagCOMPONENT pcomp,
		int dwReserved
		); // HRESULT GetDesktopItem(int nComponent,LPCOMPONENT pcomp,DWORD dwReserved);

	IntPtr  GetDesktopItemByID(          IntPtr dwID,
		ref _win32._tagCOMPONENT pcomp,
		int dwReserved
		); // HRESULT GetDesktopItemByID(DWORD dwID,LPCOMPONENT pcomp,DWORD dwReserved);

	IntPtr  GenerateDesktopItemHtml([MarshalAs(UnmanagedType.LPWStr)]string pwszFileName,
		[In] ref _win32._tagCOMPPOS pcomp,
		int dwReserved
		); // HRESULT GenerateDesktopItemHtml(LPCWSTR pwszFileName,LPCOMPONENT pcomp,DWORD dwReserved);

	IntPtr  AddUrl(          IntPtr hwnd,
		[MarshalAs(UnmanagedType.LPWStr)]
		string pszSource,
		[In] ref _win32._tagCOMPONENT pcomp,
		int dwFlags
		); // HRESULT AddUrl(HWND hwnd,LPCWSTR pszSource,LPCOMPONENT pcomp,DWORD dwFlags);

	IntPtr  GetDesktopItemBySource([MarshalAs(UnmanagedType.LPWStr)]string pszSource,
		ref _win32._tagCOMPONENT pcomp,
		int dwReserved
		); // HRESULT GetDesktopItemBySource(LPCWSTR pszSource,LPCOMPONENT pcomp,DWORD dwReserved);

}
#endregion

#region win32 consts & structs

public class _win32
{
	public const int AD_APPLY_ALL = AD_APPLY_SAVE | AD_APPLY_HTMLGEN | AD_APPLY_REFRESH;
	public const int AD_APPLY_BUFFERED_REFRESH = 0x10;
	public const int AD_APPLY_DYNAMICREFRESH = 0x20;
	public const int AD_APPLY_FORCE = 0x8;
	public const int AD_APPLY_HTMLGEN = 0x2;
	public const int AD_APPLY_REFRESH = 0x4;
	public const int AD_APPLY_SAVE = 0x1;
	public const int COMP_ELEM_ALL = COMP_ELEM_TYPE | COMP_ELEM_CHECKED | COMP_ELEM_DIRTY | COMP_ELEM_NOSCROLL | COMP_ELEM_POS_LEFT | COMP_ELEM_SIZE_WIDTH | COMP_ELEM_SIZE_HEIGHT | COMP_ELEM_POS_ZINDEX | COMP_ELEM_SOURCE | COMP_ELEM_FRIENDLYNAME | COMP_ELEM_POS_TOP | COMP_ELEM_SUBSCRIBEDURL | COMP_ELEM_ORIGINAL_CSI | COMP_ELEM_RESTORED_CSI | COMP_ELEM_CURITEMSTATE;
	public const int COMP_ELEM_CHECKED = 0x2;
	public const int COMP_ELEM_CURITEMSTATE = 0x4000;
	public const int COMP_ELEM_DIRTY = 0x4;
	public const int COMP_ELEM_FRIENDLYNAME = 0x400;
	public const int COMP_ELEM_NOSCROLL = 0x8;
	public const int COMP_ELEM_ORIGINAL_CSI = 0x1000;
	public const int COMP_ELEM_POS_LEFT = 0x10;
	public const int COMP_ELEM_POS_TOP = 0x20;
	public const int COMP_ELEM_POS_ZINDEX = 0x100;
	public const int COMP_ELEM_RESTORED_CSI = 0x2000;
	public const int COMP_ELEM_SIZE_HEIGHT = 0x80;
	public const int COMP_ELEM_SIZE_WIDTH = 0x40;
	public const int COMP_ELEM_SOURCE = 0x200;
	public const int COMP_ELEM_TYPE = 0x1;
	public const int COMP_ELEM_SUBSCRIBEDURL = 0x800;
	public const int COMP_TYPE_CONTROL = 3;
	public const int COMP_TYPE_HTMLDOC = 0;
	public const int COMP_TYPE_PICTURE = 1;
	public const int COMP_TYPE_WEBSITE = 2;
	public const int COMPONENT_DEFAULT_LEFT = (0xFFFF);
	public const int COMPONENT_DEFAULT_TOP = (0xFFFF);
	public const int IS_FULLSCREEN = 0x2;
	public const int IS_NORMAL = 0x1;
	public const int IS_SPLIT = 0x4;
	public const int MAX_PATH = 260;
	public const int WPSTYLE_CENTER = 0;
	public const int WPSTYLE_MAX = 3;
	public const int WPSTYLE_STRETCH = 2;
	public const int WPSTYLE_TILE = 1;

	[StructLayout(LayoutKind.Sequential)]
	public struct _tagCOMPSTATEINFO 
	{
		int dwSize;
		int iLeft;
		int iTop;
		int dwWidth;
		int dwHeight;
		int dwItemState;
	}

	[StructLayout(LayoutKind.Sequential)]
	public struct _tagCOMPPOS 
	{
		int dwSize;
		int iLeft;
		int iTop;
		int dwWidth;
		int dwHeight;
		int izIndex;
		[MarshalAs(UnmanagedType.Bool)]
		bool fCanResize;
		[MarshalAs(UnmanagedType.Bool)]
		bool fCanResizeX;
		[MarshalAs(UnmanagedType.Bool)]
		bool fCanResizeY;
		int iPreferredLeftPercent;
		int iPreferredTopPercent;
	}

	[StructLayout(LayoutKind.Sequential)]
	public struct _tagCOMPONENT 
	{
		public int dwSize;
		public int dwID;
		public int iComponentType;
		[MarshalAs(UnmanagedType.Bool)]
		public bool fChecked;
		[MarshalAs(UnmanagedType.Bool)]
		public bool fDirty;
		[MarshalAs(UnmanagedType.Bool)]
		public bool fNoScroll;
		public _tagCOMPPOS cpPos;
		[MarshalAs(UnmanagedType.ByValTStr, SizeConst=MAX_PATH)]
		public string wszFriendlyName;
		[MarshalAs(UnmanagedType.ByValTStr, SizeConst=2084)]
		public string wszSource;
		[MarshalAs(UnmanagedType.ByValTStr, SizeConst=2084)]
		public string wszSubscribedURL;
		public int dwCurItemState;
		public _tagCOMPSTATEINFO csiOriginal;
		public _tagCOMPSTATEINFO csiRestored;
	}

	[StructLayout(LayoutKind.Sequential)]
	public struct _tagCOMPONENTSOPT 
	{
		public int dwSize;
		[MarshalAs(UnmanagedType.Bool)]
		public bool fEnableComponents;
		[MarshalAs(UnmanagedType.Bool)]
		public bool fActiveDesktop;
	}

	[StructLayout(LayoutKind.Sequential)]
	public struct _tagWALLPAPEROPT 
	{
		public int dwSize;
		public int dwStyle;
	}
}
#endregion