图标覆盖之IShellIconOverlayIdentifier

想实现类似SVN样式的文件夹及文件的效果，即如果文件已经有改动，则需要在相应的文件图标上添加一个标志。

下面的几个连接可以提供很多参考

http://msdn.microsoft.com/en-us/library/windows/desktop/bb761265(v=vs.85).aspx

http://msdn.microsoft.com/en-us/library/windows/desktop/hh127442(v=VS.85).aspx

http://www.codeproject.com/Articles/7484/How-to-overlay-an-icon-over-existing-shell-objects

public sealed class ShellInterop
    {
        private ShellInterop()
        {
        }
        [DllImport("shell32.dll")]
        public static extern void SHChangeNotify(int eventID, uint flags, IntPtr item1, IntPtr item2);
    }

    [ComVisible(false)]
    [ComImport]
    [Guid("0C6C4200-C589-11D0-999A-00C04FD655E1")]
    [InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
    public interface IShellIconOverlayIdentifier
    {

        [PreserveSig]
        int IsMemberOf([MarshalAs(UnmanagedType.LPWStr)]string path, uint attributes);

        [PreserveSig]
        int GetOverlayInfo(
            IntPtr iconFileBuffer,
            int iconFileBufferSize,
            out int iconIndex,
            out uint flags);

        [PreserveSig]
        int GetPriority(out int priority);
    }

    [ComVisible(true)]
    [Guid("B8FA9E43-38E6-4654-8A13-FF905AD22CE5")]
    public class XavierMyIconOverlay : IShellIconOverlayIdentifier
    {

        #region IShellIconOverlayIdentifier Members
        public int IsMemberOf(string path, uint attributes)
        {
            //Show everything with icon overlay
            return 0; // S_OK
        }

        public int GetOverlayInfo(IntPtr iconFileBuffer, int iconFileBufferSize, out int iconIndex, out uint flags)
        {

            System.Diagnostics.Debug.WriteLine(string.Format("GetOverlayInfo::{0}", iconFileBuffer));

            System.Diagnostics.Debug.WriteLine(string.Format("GetOverlayInfo::{0}", iconFileBufferSize));
            string fname = @"c:\favicon.ico";

            int bytesCount = System.Text.Encoding.Unicode.GetByteCount(fname);

            System.Diagnostics.Debug.WriteLine(string.Format("GetOverlayInfo::{0}", bytesCount));

            byte[] bytes = System.Text.Encoding.Unicode.GetBytes(fname);

            if (bytes.Length + 2 < iconFileBufferSize)
            {
                for (int i = 0; i < bytes.Length; i++)
                {
                    Marshal.WriteByte(iconFileBuffer, i, bytes[i]);
                }
                //write the "\0\0"
                Marshal.WriteByte(iconFileBuffer, bytes.Length, 0);
                Marshal.WriteByte(iconFileBuffer, bytes.Length + 1, 0);
            }

            iconIndex = 0;
            flags = 1; // ISIOI_ICONFILE
            return 0; // S_OK
        }


        public int GetPriority(out int priority)
        {
            priority = 0; // 0-100 (0 is highest priority)
            return 0; // S_OK
        }
        #endregion

        #region Registry
        [ComRegisterFunction]
        public static void Register(Type t)
        {
            RegistryKey rk = Registry.LocalMachine.CreateSubKey(@"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers\_"
            + t.Name);
            rk.SetValue(string.Empty, t.GUID.ToString("B").ToUpper());
            rk.Close();
            ShellInterop.SHChangeNotify(0x08000000, 0, IntPtr.Zero, IntPtr.Zero);
        }

        [ComUnregisterFunction]
        public static void Unregister(Type t)
        {
            Registry.LocalMachine.DeleteSubKeyTree(@"SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\ShellIconOverlayIdentifiers\_"
            + t.Name);
            ShellInterop.SHChangeNotify(0x08000000, 0, IntPtr.Zero, IntPtr.Zero);
        }
        #endregion
    }

在项目属性中，选择签名，以产生程序集的强名；然后生成解决方案，会在bin目录的debug或release目录下产生xxx.dll文件

注册服务: regasm xxx.dll /codebase

重启Explorer，即可看到效果

后记:改代码还有不足，首先其编译出的Dll有版本的限制，不能同时支持64位和32位的系统，在选择生成32位的dll注册后，其仅能支持32位的程序，64位的程序不能调用该dll。如果编译成64位dll其原理一样，所以解决该问题需要把X86和x64同时注册到服务中。

在此感谢xuguilin 的帮助，http://www.cnblogs.com/xuguilin/archive/2010/04/05/1704885.html#2709859 参看该篇文章，颇有收获。同时想说CLR的代码托管机制需要更加深入的研究。

Demo：下载