C # to read "Registered File Types" icon and the reading method of the specified file icon

Apr 12 posted in DotNet (RSS), comments.

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using System;
using System.IO;
using System.Drawing;
using Microsoft.Win32;
using System.Runtime.InteropServices;


namespace GetIconDemo
{
    /// <summary>
    ///  Provides a read from the operating system icons  
    /// </summary>
    public class GetSystemIcon
    {
        /// <summary>
        ///  Pursuant to the filename to read icon, if the specified file does not exist  , NULL is returned  .
        /// </summary>
        /// <param name="fileName"></param>
        /// <returns></returns>
        public static Icon GetIconByFileName(string fileName)
        {
            if (fileName == null || fileName.Equals(string.Empty)) return null;
            if (!File.Exists(fileName)) return null;

            SHFILEINFO shinfo = new SHFILEINFO();
            //Use this to get the small Icon
            Win32.SHGetFileInfo(fileName, 0, ref shinfo, (uint)Marshal.SizeOf(shinfo), Win32.SHGFI_ICON | Win32.SHGFI_SMALLICON);
            //The icon is returned in the hIcon member of the shinfo struct
            System.Drawing.Icon myIcon = System.Drawing.Icon.FromHandle(shinfo.hIcon);
            return myIcon;
        }

        /// <summary>
        ///  Give the file name extension  (.*), Returns the corresponding icon  
        ///  If not to the "." Returns the beginning of the folder icon  .
        /// </summary>
        /// <param name="fileType"></param>
        /// <param name="isLarge"></param>
        /// <returns></returns>
        public static Icon GetIconByFileType(string fileType, bool isLarge)
        {
            if (fileType == null || fileType.Equals(string.Empty)) return null;

            RegistryKey regVersion = null;
            string regFileType = null;
            string regIconString = null;
            string systemDirectory = Environment.SystemDirectory + "\\";

            if (fileType[0] == '.')
            {
                // Read the system registry file type information  
                regVersion = Registry.ClassesRoot.OpenSubKey(fileType, true);
                if (regVersion != null)
                {
                    regFileType = regVersion.GetValue("") as string;
                    regVersion.Close();
                    regVersion = Registry.ClassesRoot.OpenSubKey(regFileType + @"\DefaultIcon", true);
                    if (regVersion != null)
                    {
                        regIconString = regVersion.GetValue("") as string;
                        regVersion.Close();
                    }
                }
                if (regIconString == null)
                {
                    // No read to a file type registration information, specified as an unknown file type icons  
                    regIconString = systemDirectory + "shell32.dll,0";
                }
            }
            else
            {
                // Directly specified as the folder icon  
                regIconString = systemDirectory + "shell32.dll,3";
            }
            string[] fileIcon = regIconString.Split(new char[] { ',' });
            if (fileIcon.Length != 2)
            {
                // System registry of plotting cannot directly extract, it returns the executable's universal icon  
                fileIcon = new string[] { systemDirectory + "shell32.dll", "2" };
            }
            Icon resultIcon = null;
            try
            {
                // Call the API method to read icon  
                int[] phiconLarge = new int[1];
                int[] phiconSmall = new int[1];
                uint count = Win32.ExtractIconEx(fileIcon[0], Int32.Parse(fileIcon[1]), phiconLarge, phiconSmall, 1);
                IntPtr IconHnd = new IntPtr(isLarge ? phiconLarge[0] : phiconSmall[0]);
                resultIcon = Icon.FromHandle(IconHnd);
            }
            catch { }
            return resultIcon;
        }
    }



    [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>
    ///  Definition of API method called  
    /// </summary>
    class Win32
    {
        public const uint SHGFI_ICON = 0x100;
        public const uint SHGFI_LARGEICON = 0x0; // 'Large icon
        public const uint SHGFI_SMALLICON = 0x1; // 'Small icon

        [DllImport("shell32.dll")]
        public static extern IntPtr SHGetFileInfo(string pszPath, uint dwFileAttributes, ref SHFILEINFO psfi, uint cbSizeFileInfo, uint uFlags);
        [DllImport("shell32.dll")]
        public static extern uint ExtractIconEx(string lpszFile, int nIconIndex, int[] phiconLarge, int[] phiconSmall, uint nIcons);

    }
}


 This article from CSDN blog  , Reprinted, with the citation  :http://blog.csdn.net/snlei/archive/2009/03/08/3970345.aspx