c# 使用ActiveDesktop实现壁纸切换，适合大部分图片格式

操作步骤：

首先添加类：

using System;
using System.Runtime.InteropServices;

namespace WorkHelper
{
enum WPSTYLE
{
CENTER = 0,
TILE = 1,
STRETCH = 2,
MAX = 3
}

struct WALLPAPEROPT
{
public int dwSize;
public WPSTYLE dwStyle;
}

struct COMPONENTSOPT
{
public int dwSize;
[MarshalAs(UnmanagedType.Bool)]
public bool fEnableComponents;
[MarshalAs(UnmanagedType.Bool)]
public bool fActiveDesktop;
}

struct COMPPOS
{
public const int COMPONENT_TOP = 0x3FFFFFFF;
public const int COMPONENT_DEFAULT_LEFT = 0xFFFF;
public const int COMPONENT_DEFAULT_TOP = 0xFFFF;

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

[Flags]
enum ITEMSTATE
{
NORMAL = 0x00000001,
FULLSCREEN = 00000002,
SPLIT = 0x00000004,
VALIDSIZESTATEBITS = NORMAL | SPLIT | FULLSCREEN,
VALIDSTATEBITS = NORMAL | SPLIT | FULLSCREEN | unchecked((int)0x80000000) | 0x40000000
}

struct COMPSTATEINFO
{
public int dwSize;
public int iLeft;
public int iTop;
public int dwWidth;
public int dwHeight;
public int dwItemState;
}

enum COMP_TYPE
{
HTMLDOC = 0,
PICTURE = 1,
WEBSITE = 2,
CONTROL = 3,
CFHTML = 4,
MAX = 4
}

[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
struct COMPONENT
{
private const int INTERNET_MAX_URL_LENGTH = 2084;   //   =
// INTERNET_MAX_SCHEME_LENGTH   (32)   +   "://\0".Length   +
// INTERNET_MAX_PATH_LENGTH   (2048)

public int dwSize;
public int dwID;
public COMP_TYPE iComponentType;
[MarshalAs(UnmanagedType.Bool)]
public bool fChecked;
[MarshalAs(UnmanagedType.Bool)]
public bool fDirty;
[MarshalAs(UnmanagedType.Bool)]
public bool fNoScroll;
public COMPPOS cpPos;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string wszFriendlyName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = INTERNET_MAX_URL_LENGTH)]
public string wszSource;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = INTERNET_MAX_URL_LENGTH)]
public string wszSubscribedURL;

#if   AD_IE5
public   int   dwCurItemState;
public   COMPSTATEINFO   csiOriginal;
public   COMPSTATEINFO   csiRestored;
#endif
}

enum DTI_ADTIWUI
{
DTI_ADDUI_DEFAULT = 0x00000000,
DTI_ADDUI_DISPSUBWIZARD = 0x00000001,
DTI_ADDUI_POSITIONITEM = 0x00000002,
}

[Flags]
enum AD_APPLY
{
SAVE = 0x00000001,
HTMLGEN = 0x00000002,
REFRESH = 0x00000004,
ALL = SAVE | HTMLGEN | REFRESH,
FORCE = 0x00000008,
BUFFERED_REFRESH = 0x00000010,
DYNAMICREFRESH = 0x00000020
}

[Flags]
enum COMP_ELEM
{
TYPE = 0x00000001,
CHECKED = 0x00000002,
DIRTY = 0x00000004,
NOSCROLL = 0x00000008,
POS_LEFT = 0x00000010,
POS_TOP = 0x00000020,
SIZE_WIDTH = 0x00000040,
SIZE_HEIGHT = 0x00000080,
POS_ZINDEX = 0x00000100,
SOURCE = 0x00000200,
FRIENDLYNAME = 0x00000400,
SUBSCRIBEDURL = 0x00000800,
ORIGINAL_CSI = 0x00001000,
RESTORED_CSI = 0x00002000,
CURITEMSTATE = 0x00004000,
ALL = TYPE | CHECKED | DIRTY | NOSCROLL | POS_LEFT | SIZE_WIDTH |
SIZE_HEIGHT | POS_ZINDEX | SOURCE |
FRIENDLYNAME | POS_TOP | SUBSCRIBEDURL | ORIGINAL_CSI |
RESTORED_CSI | CURITEMSTATE
}

[Flags]
enum ADDURL
{
SILENT = 0x0001
}

[
ComImport(),
Guid("F490EB00-1240-11D1-9888-006097DEACF9"),
InterfaceType(ComInterfaceType.InterfaceIsIUnknown)
]
interface IActiveDesktop
{
void ApplyChanges(AD_APPLY dwFlags);
void GetWallpaper([MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder pwszWallpaper, int cchWallpaper, int dwReserved);
void SetWallpaper([MarshalAs(UnmanagedType.LPWStr)]   string pwszWallpaper, int dwReserved);
void GetWallpaperOptions(ref   WALLPAPEROPT pwpo, int dwReserved);
void SetWallpaperOptions([In]   ref   WALLPAPEROPT pwpo, int dwReserved);
void GetPattern([MarshalAs(UnmanagedType.LPWStr)] System.Text.StringBuilder pwszPattern, int cchPattern, int dwReserved);
void SetPattern([MarshalAs(UnmanagedType.LPWStr)]   string pwszPattern, int dwReserved);
void GetDesktopItemOptions(ref   COMPONENTSOPT pco, int dwReserved);
void SetDesktopItemOptions([In]   ref   COMPONENTSOPT pco, int dwReserved);
void AddDesktopItem([In]   ref   COMPONENT pcomp, int dwReserved);
void AddDesktopItemWithUI(IntPtr hwnd, [In]   ref   COMPONENT pcomp, DTI_ADTIWUI dwFlags);
void ModifyDesktopItem([In]   ref   COMPONENT pcomp, COMP_ELEM dwFlags);
void RemoveDesktopItem([In]   ref   COMPONENT pcomp, int dwReserved);
void GetDesktopItemCount(out   int lpiCount, int dwReserved);
void GetDesktopItem(int nComponent, ref   COMPONENT pcomp, int dwReserved);
void GetDesktopItemByID(IntPtr dwID, ref   COMPONENT pcomp, int dwReserved);
void GenerateDesktopItemHtml([MarshalAs(UnmanagedType.LPWStr)] string pwszFileName, [In]   ref   COMPONENT pcomp, int dwReserved);
void AddUrl(IntPtr hwnd, [MarshalAs(UnmanagedType.LPWStr)]   string pszSource, [In]   ref   COMPONENT pcomp, ADDURL dwFlags);
void GetDesktopItemBySource([MarshalAs(UnmanagedType.LPWStr)] string pwszSource, ref   COMPONENT pcomp, int dwReserved);
}

[
ComImport(),
Guid("75048700-EF1F-11D0-9888-006097DEACF9")
]
class ActiveDesktop   /*   :   IActiveDesktop   */   { }
}

调用：（终于搞定背景图片样式了）

public bool SetDeskBg(String filename)
{
try
{
ActiveDesktop ad = new ActiveDesktop();
IActiveDesktop iad = ad as IActiveDesktop;
if (iad != null)
{
//WPSTYLE_CENTER 居中 0
//WPSTYLE_TILE 平铺 1
//WPSTYLE_STRETCH 拉伸 2
WPSTYLE dwstyle = WPSTYLE.STRETCH;//这里调整显示背景图片样式
WALLPAPEROPT wp = new WALLPAPEROPT();
wp.dwSize = System.Runtime.InteropServices.Marshal.SizeOf(wp);
wp.dwStyle = dwstyle;
iad.SetWallpaperOptions(ref wp, 0);

iad.SetWallpaper(filename, 0);
iad.ApplyChanges(AD_APPLY.ALL);
System.Runtime.InteropServices.Marshal.ReleaseComObject(ad);
ad = null;
}
return true;
}
catch
{
return false;
}
}