C#获取文件(磁盘驱动器)的关联图标（使用API SHGetFileInfo）

这是一个C#调用系统API SHGetFileInfo 的一个演示例子，也是给一位网友的答复，先看效果图：

SHGetFileInfo 这个API， 可以获取指定对象的非常详细的相关信息，具体的内容，大家可以MSDN上关于此API的说明。

这个获取关联图标，可以获取磁盘分区的图标，可以获取某个特定类型的文件的图标，也可以获取某个指定文件的图标，下面给出实现的全部代码：

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/// <summary>
/// 保存文件信息的结构体
/// </summary>
/// 
[StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto)]
struct SHFILEINFO
{
    public IntPtr hIcon;
    public int iIcon;
    public uint dwAttributes;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
    public string szDisplayName;
    [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
    public string szTypeName;
}

class NativeMethods
{

    [DllImport("Shell32.dll", EntryPoint = "SHGetFileInfo", SetLastError = true, CharSet = CharSet.Auto)]
    public static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, uint cbFileInfo, uint uFlags);

    [DllImport("User32.dll", EntryPoint = "DestroyIcon")]
    public static extern int DestroyIcon(IntPtr hIcon);

    #region API 参数的常量定义

    public const uint SHGFI_ICON = 0x100;
    public const uint SHGFI_LARGEICON = 0x0; //大图标 32×32
    public const uint SHGFI_SMALLICON = 0x1; //小图标 16×16
    public const uint SHGFI_USEFILEATTRIBUTES = 0x10;

    #endregion

}
/// <summary>
/// 获取文件类型的关联图标
/// </summary>
/// <param name="fileName">文件类型的扩展名或文件的绝对路径</param>
/// <param name="isLargeIcon">是否返回大图标</param>
/// <returns>获取到的图标</returns>
static Icon GetIcon(string fileName, bool isLargeIcon)
{
    SHFILEINFO shfi = new SHFILEINFO();
    IntPtr hI;

    if (isLargeIcon)
        hI = NativeMethods.SHGetFileInfo(fileName, 0, ref shfi, (uint)Marshal.SizeOf(shfi), NativeMethods.SHGFI_ICON | NativeMethods.SHGFI_USEFILEATTRIBUTES | NativeMethods.SHGFI_LARGEICON);
    else
        hI = NativeMethods.SHGetFileInfo(fileName, 0, ref shfi, (uint)Marshal.SizeOf(shfi), NativeMethods.SHGFI_ICON | NativeMethods.SHGFI_USEFILEATTRIBUTES | NativeMethods.SHGFI_SMALLICON);

    Icon icon = Icon.FromHandle(shfi.hIcon).Clone() as Icon;

    NativeMethods.DestroyIcon(shfi.hIcon); //释放资源
    return icon;
}

private void linkLabel1_LinkClicked(object sender, LinkLabelLinkClickedEventArgs e)
{
    Help.ShowHelp(this, "http://www.zu14.cn");
}

private void btnGetIcon_Click(object sender, EventArgs e)
{
    using (Graphics g = this.pbSmallIcon.CreateGraphics())
    {
        g.Clear(this.pbSmallIcon.BackColor); //清除picturebox的背景色，为了画透明图标

        g.DrawIcon(GetIcon(this.tbFileExt.Text, false), 1, 1); //绘制小图标
    }

    using (Graphics g = this.pbLargeIcon.CreateGraphics())
    {
        g.Clear(this.pbLargeIcon.BackColor); //清除picturebox的背景色，为了画透明图标

        g.DrawIcon(GetIcon(this.tbFileExt.Text, true), 1, 1); //绘制小图标
    }
}