封装：Windows系统文件图标

用途：用于获取文件系统默认图标

using System;
using System.Collections.Generic;
using System.Drawing;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;
using System.Text;

namespace HebianGu.ComLibModule.API
{

/// <summary> 获取文件关联图标 </summary>
public partial class IconHelper
{
/// <summary> 返回系统设置的图标 </summary>
/// <param name="pszPath">文件路径 如果为"" 返回文件夹的</param>
/// <param name="dwFileAttributes">0</param>
/// <param name="psfi">结构体</param>
/// <param name="cbSizeFileInfo">结构体大小</param>
/// <param name="uFlags">枚举类型</param>
/// <returns>-1失败</returns>
[DllImport("shell32.dll")]
public static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, uint cbSizeFileInfo, uint uFlags);

/// <summary> 获取文件图标 </summary>
public Icon GetFileIcon(string p_Path)
{
SHFILEINFO _SHFILEINFO = new SHFILEINFO();
IntPtr _IconIntPtr = SHGetFileInfo(p_Path, 0, ref _SHFILEINFO, (uint)Marshal.SizeOf(_SHFILEINFO), (uint)(SHGFI.SHGFI_ICON | SHGFI.SHGFI_LARGEICON | SHGFI.SHGFI_USEFILEATTRIBUTES));
if (_IconIntPtr.Equals(IntPtr.Zero)) return null;
Icon _Icon = System.Drawing.Icon.FromHandle(_SHFILEINFO.hIcon);
return _Icon;
}

/// <summary> 获取文件夹图标 </summary>
public Icon GetDirectoryIcon()
{
SHFILEINFO _SHFILEINFO = new SHFILEINFO();
IntPtr _IconIntPtr = SHGetFileInfo(@"", 0, ref _SHFILEINFO, (uint)Marshal.SizeOf(_SHFILEINFO), (uint)(SHGFI.SHGFI_ICON | SHGFI.SHGFI_LARGEICON));
if (_IconIntPtr.Equals(IntPtr.Zero)) return null;
Icon _Icon = System.Drawing.Icon.FromHandle(_SHFILEINFO.hIcon);
return _Icon;
}

/// <summary> 获取系统图标 </summary>
public Icon GetSystemInfoIcon(string p_Path)
{
if (Path.HasExtension(p_Path))
{
try
{
return Icon.ExtractAssociatedIcon(p_Path);
}
catch
{
return null;
}

}
else
{
return this.GetDirectoryIcon();
}
}

}

partial class IconHelper
{
#region - Start 单例模式 -

/// <summary> 单例模式 </summary>
private static IconHelper t = null;

/// <summary> 多线程锁 </summary>
private static object localLock = new object();

/// <summary> 创建指定对象的单例实例 </summary>
public static IconHelper Instance
{
get
{
if (t == null)
{
lock (localLock)
{
if (t == null)
return t = new IconHelper();
}
}
return t;
}
}
/// <summary> 禁止外部实例 </summary>
private IconHelper()
{

}
#endregion - 单例模式 End -

}

[StructLayout(LayoutKind.Sequential)]
public struct SHFILEINFO
{
public IntPtr hIcon;
public IntPtr iIcon;
public uint dwAttributes;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 260)]
public string szDisplayName;
[MarshalAs(UnmanagedType.ByValTStr, SizeConst = 80)]
public string szTypeName;
}

public enum SHGFI
{
SHGFI_ICON = 0x100,
SHGFI_LARGEICON = 0x0,
SHGFI_USEFILEATTRIBUTES = 0x10
}
}


应用示例：
/// <summary> 图片路径 </summary>
public Icon ImagePath
{
get { return IconHelper.Instance.GetSystemInfoIcon(FilePath); }
}