1.根据文件路径文件或文件夹图标获取 2.根据后缀获取系统图标

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

namespace CommonLibrary
{
/// <summary>
/// 根据文件名称获取文件的系统图标
/// </summary>
public static class IconUtilsByFilePath
{
[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;
}

///<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);

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

///<summary>
/// 获取文件图标 zgke@sina.com qq:116149
///</summary>
///<param name="p_Path">文件全路径</param>
///<returns>图标</returns>
public static 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  zgke@sina.com qq:116149
///</summary>
///<returns>图标</returns>
public static 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>
/// 根据文件的后缀获取文件的系统图标
/// </summary>
public static class IconUtilsByExtension
{

///<summary>

/// Used to access system folder icons.

///</summary>

///<param name="largeIcon">Specify large or small icons.</param>

///<param name="openFolder">Specify open or closed FolderType.</param>

///<returns>The requested Icon.</returns>

public static Icon GetIconForFolder(Boolean largeIcon, Boolean openFolder)
{

SHFILEINFO shellFileInfo = new SHFILEINFO();

try
{

uint flags = SHGFI_ICON | SHGFI_USEFILEATTRIBUTES;

flags |= openFolder ? SHGFI_OPENICON : 0;

flags |= largeIcon ? SHGFI_LARGEICON : SHGFI_SMALLICON;

SHGetFileInfo(null,

FILE_ATTRIBUTE_DIRECTORY,

ref shellFileInfo,

(uint)Marshal.SizeOf(shellFileInfo),

flags);

return (Icon)Icon.FromHandle(shellFileInfo.hIcon).Clone();

}

finally
{

DestroyIcon(shellFileInfo.hIcon);        // Cleanup

}

}

///<summary>

/// Used to access file icons for a given extension.

///</summary>

///<param name="extension">The file extension to get the icon for.</param>

///<param name="largeIcon">Specify large or small icons.</param>

///<param name="linkOverlay">Specify link overlay on the icon.</param>

///<returns>The requested Icon</returns>

public static Icon GetIconForFileExtension(String extension, Boolean largeIcon, Boolean linkOverlay)
{

if (!extension.StartsWith("."))

extension = "." + extension;

SHFILEINFO shellFileInfo = new SHFILEINFO();

try
{

uint flags = SHGFI_ICON | SHGFI_USEFILEATTRIBUTES;

flags |= linkOverlay ? SHGFI_LINKOVERLAY : 0;

flags |= largeIcon ? SHGFI_LARGEICON : SHGFI_SMALLICON;

SHGetFileInfo(extension,

FILE_ATTRIBUTE_NORMAL,

ref shellFileInfo,

(uint)Marshal.SizeOf(shellFileInfo),

flags);

return (Icon)Icon.FromHandle(shellFileInfo.hIcon).Clone();

}

finally
{

DestroyIcon(shellFileInfo.hIcon);

}

}

#region P/Invoke

private const int MAX_PATH = 256;

private const uint SHGFI_ICON = 0x000000100;

private const uint SHGFI_LINKOVERLAY = 0x000008000;

private const uint SHGFI_LARGEICON = 0x000000000;

private const uint SHGFI_SMALLICON = 0x000000001;

private const uint SHGFI_OPENICON = 0x000000002;

private const uint SHGFI_USEFILEATTRIBUTES = 0x000000010;

private const uint FILE_ATTRIBUTE_DIRECTORY = 0x00000010;

private const uint FILE_ATTRIBUTE_NORMAL = 0x00000080;

[StructLayout(LayoutKind.Sequential)]

private struct SHFILEINFO
{

public const int NAMESIZE = 80;

public IntPtr hIcon;

public int iIcon;

public uint dwAttributes;

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = MAX_PATH)]

public string szDisplayName;

[MarshalAs(UnmanagedType.ByValTStr, SizeConst = NAMESIZE)]

public string szTypeName;

};

[DllImport("Shell32.dll")]

private static extern IntPtr SHGetFileInfo(

string pszPath,

uint dwFileAttributes,

ref SHFILEINFO psfi,

uint cbFileInfo,

uint uFlags

);

[DllImport("User32.dll")]

private static extern int DestroyIcon(IntPtr hIcon);

#endregion
}
}