[转贴]按文件类型获取其图标

原帖地址：http://tianfang.cnblogs.com/

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Runtime.InteropServices;

namespace IconHelper
{
    /**//// <summary>
    /// Provides static methods to read system icons for both folders and files.
    /// </summary>
    /// <example>
    /// <code>IconReader.GetFileIcon("c:\\general.xls");</code>
    /// </example>
    public class IconReader
    {
        /**//// <summary>
        /// Options to specify the size of icons to return.
        /// </summary>
        public enum IconSize
        {
            /**//// <summary>
            /// Specify large icon - 32 pixels by 32 pixels.
            /// </summary>
            Large = 0,
            /**//// <summary>
            /// Specify small icon - 16 pixels by 16 pixels.
            /// </summary>
            Small = 1
        }

        /**//// <summary>
        /// Options to specify whether folders should be in the open or closed state.
        /// </summary>
        public enum FolderType
        {
            /**//// <summary>
            /// Specify open folder.
            /// </summary>
            Open = 0,
            /**//// <summary>
            /// Specify closed folder.
            /// </summary>
            Closed = 1
        }

        /**//// <summary>
        /// Returns an icon for a given file - indicated by the name parameter.
        /// </summary>
        /// <param name="name">Pathname for file.</param>
        /// <param name="size">Large or small</param>
        /// <param name="linkOverlay">Whether to include the link icon</param>
        /// <returns>System.Drawing.Icon</returns>
        public static System.Drawing.Icon GetFileIcon(string name, IconSize size, bool linkOverlay)
        {
            Shell32.SHFILEINFO shfi = new Shell32.SHFILEINFO();
            uint flags = Shell32.SHGFI_ICON | Shell32.SHGFI_USEFILEATTRIBUTES;

            if (true == linkOverlay) flags += Shell32.SHGFI_LINKOVERLAY;

            /**//* Check the size specified for return. */
            if (IconSize.Small == size)
            {
                flags += Shell32.SHGFI_SMALLICON;
            }
            else
            {
                flags += Shell32.SHGFI_LARGEICON;
            }

            Shell32.SHGetFileInfo(name,
                Shell32.FILE_ATTRIBUTE_NORMAL,
                ref shfi,
                (uint)System.Runtime.InteropServices.Marshal.SizeOf(shfi),
                flags);

            // Copy (clone) the returned icon to a new object, thus allowing us to clean-up properly
            System.Drawing.Icon icon = (System.Drawing.Icon)System.Drawing.Icon.FromHandle(shfi.hIcon).Clone();
            User32.DestroyIcon(shfi.hIcon);        // Cleanup
            return icon;
        }

        /**//// <summary>
        /// Used to access system folder icons.
        /// </summary>
        /// <param name="size">Specify large or small icons.</param>
        /// <param name="folderType">Specify open or closed FolderType.</param>
        /// <returns>System.Drawing.Icon</returns>
        public static System.Drawing.Icon GetFolderIcon(IconSize size, FolderType folderType)
        {
            // Need to add size check, although errors generated at present!
            uint flags = Shell32.SHGFI_ICON | Shell32.SHGFI_USEFILEATTRIBUTES;

            if (FolderType.Open == folderType)
            {
                flags += Shell32.SHGFI_OPENICON;
            }

            if (IconSize.Small == size)
            {
                flags += Shell32.SHGFI_SMALLICON;
            }
            else
            {
                flags += Shell32.SHGFI_LARGEICON;
            }

            // Get the folder icon
            Shell32.SHFILEINFO shfi = new Shell32.SHFILEINFO();
            Shell32.SHGetFileInfo(null,
                Shell32.FILE_ATTRIBUTE_DIRECTORY,
                ref shfi,
                (uint)System.Runtime.InteropServices.Marshal.SizeOf(shfi),
                flags);

            System.Drawing.Icon.FromHandle(shfi.hIcon);    // Load the icon from an HICON handle

            // Now clone the icon, so that it can be successfully stored in an ImageList
            System.Drawing.Icon icon = (System.Drawing.Icon)System.Drawing.Icon.FromHandle(shfi.hIcon).Clone();

            User32.DestroyIcon(shfi.hIcon);        // Cleanup
            return icon;
        }
    }

    /**//// <summary>
    /// Wraps necessary Shell32.dll structures and functions required to retrieve Icon Handles using SHGetFileInfo. Code
    /// courtesy of MSDN Cold Rooster Consulting case study.
    /// </summary>
    /// 

    // This code has been left largely untouched from that in the CRC example. The main changes have been moving
    // the icon reading code over to the IconReader type.
    public class Shell32
    {

        public const int MAX_PATH = 256;
        [StructLayout(LayoutKind.Sequential)]
            public struct SHITEMID
        {
            public ushort cb;
            [MarshalAs(UnmanagedType.LPArray)]
            public byte[] abID;
        }

        [StructLayout(LayoutKind.Sequential)]
            public struct ITEMIDLIST
        {
            public SHITEMID mkid;
        }

        [StructLayout(LayoutKind.Sequential)]
            public struct BROWSEINFO
        {
            public IntPtr hwndOwner;
            public IntPtr pidlRoot;
            public IntPtr pszDisplayName;
            [MarshalAs(UnmanagedType.LPTStr)]
            public string lpszTitle;
            public uint ulFlags;
            public IntPtr lpfn;
            public int lParam;
            public IntPtr iImage;
        }

        // Browsing for directory.
        public const uint BIF_RETURNONLYFSDIRS = 0x0001;
        public const uint BIF_DONTGOBELOWDOMAIN = 0x0002;
        public const uint BIF_STATUSTEXT = 0x0004;
        public const uint BIF_RETURNFSANCESTORS = 0x0008;
        public const uint BIF_EDITBOX = 0x0010;
        public const uint BIF_VALIDATE = 0x0020;
        public const uint BIF_NEWDIALOGSTYLE = 0x0040;
        public const uint BIF_USENEWUI = (BIF_NEWDIALOGSTYLE | BIF_EDITBOX);
        public const uint BIF_BROWSEINCLUDEURLS = 0x0080;
        public const uint BIF_BROWSEFORCOMPUTER = 0x1000;
        public const uint BIF_BROWSEFORPRINTER = 0x2000;
        public const uint BIF_BROWSEINCLUDEFILES = 0x4000;
        public const uint BIF_SHAREABLE = 0x8000;

        [StructLayout(LayoutKind.Sequential)]
            public 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;
        };

        public const uint SHGFI_ICON = 0x000000100;     // get icon
        public const uint SHGFI_DISPLAYNAME = 0x000000200;     // get display name
        public const uint SHGFI_TYPENAME = 0x000000400;     // get type name
        public const uint SHGFI_ATTRIBUTES = 0x000000800;     // get attributes
        public const uint SHGFI_ICONLOCATION = 0x000001000;     // get icon location
        public const uint SHGFI_EXETYPE = 0x000002000;     // return exe type
        public const uint SHGFI_SYSICONINDEX = 0x000004000;     // get system icon index
        public const uint SHGFI_LINKOVERLAY = 0x000008000;     // put a link overlay on icon
        public const uint SHGFI_SELECTED = 0x000010000;     // show icon in selected state
        public const uint SHGFI_ATTR_SPECIFIED = 0x000020000;     // get only specified attributes
        public const uint SHGFI_LARGEICON = 0x000000000;     // get large icon
        public const uint SHGFI_SMALLICON = 0x000000001;     // get small icon
        public const uint SHGFI_OPENICON = 0x000000002;     // get open icon
        public const uint SHGFI_SHELLICONSIZE = 0x000000004;     // get shell size icon
        public const uint SHGFI_PIDL = 0x000000008;     // pszPath is a pidl
        public const uint SHGFI_USEFILEATTRIBUTES = 0x000000010;     // use passed dwFileAttribute
        public const uint SHGFI_ADDOVERLAYS = 0x000000020;     // apply the appropriate overlays
        public const uint SHGFI_OVERLAYINDEX = 0x000000040;     // Get the index of the overlay

        public const uint FILE_ATTRIBUTE_DIRECTORY = 0x00000010;
        public const uint FILE_ATTRIBUTE_NORMAL = 0x00000080;

        [DllImport("Shell32.dll")]
        public static extern IntPtr SHGetFileInfo(
            string pszPath,
            uint dwFileAttributes,
            ref SHFILEINFO psfi,
            uint cbFileInfo,
            uint uFlags
            );
    }

    /**//// <summary>
    /// Wraps necessary functions imported from User32.dll. Code courtesy of MSDN Cold Rooster Consulting example.
    /// </summary>
    public class User32
    {
        /**//// <summary>
        /// Provides access to function required to delete handle. This method is used internally
        /// and is not required to be called separately.
        /// </summary>
        /// <param name="hIcon">Pointer to icon handle.</param>
        /// <returns>N/A</returns>
        [DllImport("User32.dll")]
        public static extern int DestroyIcon(IntPtr hIcon);
    }
}