Windows7获取、更换桌面背景，C#

可以使用C#中的SystemParametersInfo函数来获取和更换Windows桌面背景。具体步骤如下：

1. 获取当前桌面背景路径：

StringBuilder sb = new StringBuilder(256);
bool result = SystemParametersInfo(SPI_GETDESKWALLPAPER, 256, sb, 0);
if (result)
{
    string path = sb.ToString();
}

2. 更换桌面背景：

bool result = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, "newImagePath", SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
if (!result)
{
    // 更换桌面背景失败
}

其中，`SPI_SETDESKWALLPAPER`表示设置桌面背景，`SPI_GETDESKWALLPAPER`表示获取当前桌面背景。

`SPIF_UPDATEINIFILE`和`SPIF_SENDWININICHANGE`是一些标志位，用于更新系统设置并立即生效。

需要引入以下命名空间：

using System.Runtime.InteropServices;
using System.Text;

完整代码示例：

using System.Runtime.InteropServices;
using System.Text;

public class DesktopBackground
{
    [DllImport("user32.dll", CharSet = CharSet.Auto)]
    private static extern int SystemParametersInfo(int uAction, int uParam, StringBuilder lpvParam, int fuWinIni);

    private const int SPI_GETDESKWALLPAPER = 0x0073;
    private const int SPI_SETDESKWALLPAPER = 0x0014;
    private const int SPIF_UPDATEINIFILE = 0x01;
    private const int SPIF_SENDWININICHANGE = 0x02;

    public static string GetDesktopBackground()
    {
        StringBuilder sb = new StringBuilder(256);
        bool result = SystemParametersInfo(SPI_GETDESKWALLPAPER, 256, sb, 0);
        if (result)
        {
            return sb.ToString();
        }
        else
        {
            return null;
        }
    }

    public static bool SetDesktopBackground(string imagePath)
    {
        bool result = SystemParametersInfo(SPI_SETDESKWALLPAPER, 0, imagePath, SPIF_UPDATEINIFILE | SPIF_SENDWININICHANGE);
        return result;
    }
}