C# WinForm 选择文件夹对话框

选择文件夹只有选择 FolderBrowserDialog，这种选择对话框让人有些抓狂，特别当文件目录比较深、需要多次选择文件夹操作时。

参考：自定义文件夹选择对话框 - 我也是个傻瓜 - 博客园 (cnblogs.com)

using System;
using System.IO;
using System.Runtime.CompilerServices;
using System.Runtime.InteropServices;
using System.Runtime.InteropServices.ComTypes;
using System.Security;
using System.Windows.Forms;

public class SelectFolderDialog
{
    #region Internal Enums

    internal enum FDAP
    {
        FDAP_BOTTOM = 0,
        FDAP_TOP = 1
    }

    internal enum FDE_OVERWRITE_RESPONSE
    {
        FDEOR_DEFAULT = 0x00000000,
        FDEOR_ACCEPT = 0x00000001,
        FDEOR_REFUSE = 0x00000002
    }

    internal enum FDE_SHAREVIOLATION_RESPONSE
    {
        FDESVR_DEFAULT = 0x00000000,
        FDESVR_ACCEPT = 0x00000001,
        FDESVR_REFUSE = 0x00000002
    }

    [Flags]
    internal enum FOS : uint
    {
        FOS_OVERWRITEPROMPT = 0x00000002,
        FOS_STRICTFILETYPES = 0x00000004,
        FOS_NOCHANGEDIR = 0x00000008,
        FOS_PICKFOLDERS = 0x00000020,
        FOS_FORCEFILESYSTEM = 0x00000040, // Ensure that items returned are filesystem items.
        FOS_ALLNONSTORAGEITEMS = 0x00000080, // Allow choosing items that have no storage.
        FOS_NOVALIDATE = 0x00000100,
        FOS_ALLOWMULTISELECT = 0x00000200,
        FOS_PATHMUSTEXIST = 0x00000800,
        FOS_FILEMUSTEXIST = 0x00001000,
        FOS_CREATEPROMPT = 0x00002000,
        FOS_SHAREAWARE = 0x00004000,
        FOS_NOREADONLYRETURN = 0x00008000,
        FOS_NOTESTFILECREATE = 0x00010000,
        FOS_HIDEMRUPLACES = 0x00020000,
        FOS_HIDEPINNEDPLACES = 0x00040000,
        FOS_NODEREFERENCELINKS = 0x00100000,
        FOS_DONTADDTORECENT = 0x02000000,
        FOS_FORCESHOWHIDDEN = 0x10000000,
        FOS_DEFAULTNOMINIMODE = 0x20000000
    }

    internal enum SIATTRIBFLAGS
    {
        SIATTRIBFLAGS_AND = 1,
        SIATTRIBFLAGS_APPCOMPAT = 3,
        SIATTRIBFLAGS_OR = 2
    }

    internal enum SIGDN : uint
    {
        SIGDN_DESKTOPABSOLUTEEDITING = 0x8004c000,
        SIGDN_DESKTOPABSOLUTEPARSING = 0x80028000,
        SIGDN_FILESYSPATH = 0x80058000,
        SIGDN_NORMALDISPLAY = 0,
        SIGDN_PARENTRELATIVE = 0x80080001,
        SIGDN_PARENTRELATIVEEDITING = 0x80031001,
        SIGDN_PARENTRELATIVEFORADDRESSBAR = 0x8007c001,
        SIGDN_PARENTRELATIVEPARSING = 0x80018001,
        SIGDN_URL = 0x80068000
    }

    #endregion Internal Enums

    #region 公共属性

    /// <summary>
    /// 文件
    /// </summary>
    public string Folder { get; set; }
    /// <summary>
    /// 标题
    /// </summary>
    public string Title { get; set; }

    #endregion 公共属性

    #region 公共方法
    /// <summary>
    /// 显示对话框架
    /// </summary>
    /// <param name="owner"></param>
    /// <returns></returns>

    public DialogResult ShowDialog(IWin32Window owner = null)
    {
        IntPtr hwndOwner = owner != null ? owner.Handle : NativeMethods.GetActiveWindow();
        NativeInterfaces.IFileOpenDialog dialog = (NativeInterfaces.IFileOpenDialog)new FileOpenDialog();
        try
        {
            if (!string.IsNullOrEmpty(Folder))
            {
                if (!IsValidFolderPath(Folder))
                {
                    // 提示用户文件夹路径无效
                    MessageBox.Show("无效的文件夹路径，请重新选择。", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error);
                    return DialogResult.Cancel;
                }

                Guid _shellItemGuid = typeof(NativeInterfaces.IShellItem).GUID;
                NativeInterfaces.IShellItem item = (NativeInterfaces.IShellItem)NativeMethods.SHCreateItemFromParsingName(Folder, null, ref _shellItemGuid);
                if (item != null)
                    dialog.SetFolder(item);
            }

            dialog.SetOptions(FOS.FOS_PICKFOLDERS | FOS.FOS_FORCEFILESYSTEM);

            if (!string.IsNullOrEmpty(Title))
                dialog.SetTitle(Title);

            int hr = dialog.Show(hwndOwner);
            if (hr == NativeMethods.ERROR_CANCELLED)
                return DialogResult.Cancel;

            if (hr != 0)
                return DialogResult.Abort;

            NativeInterfaces.IShellItem resultItem;
            dialog.GetResult(out resultItem);

            resultItem.GetDisplayName(SIGDN.SIGDN_FILESYSPATH, out string path);
            Folder = path;

            return DialogResult.OK;
        }
        catch (Exception ex)
        {
            // 处理异常
            MessageBox.Show($"发生错误：{ex.Message}", "错误", MessageBoxButtons.OK, MessageBoxIcon.Error);
            return DialogResult.Abort;
        }
    }

    private bool IsValidFolderPath(string folderPath)
    {
        // 这里可以添加更复杂的逻辑来验证文件夹路径的有效性
        // 例如，检查文件夹是否存在，是否可访问等
        return Directory.Exists(folderPath);
    }

    #endregion 公共方法

    #region Internal Structs

    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Auto, Pack = 4)]
    internal struct COMDLG_FILTERSPEC
    {
        [MarshalAs(UnmanagedType.LPWStr)]
        public string pszName;

        [MarshalAs(UnmanagedType.LPWStr)]
        public string pszSpec;
    }

    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    internal struct PROPERTYKEY
    {
        public Guid fmtid;

        public uint pid;
    }

    #endregion Internal Structs

    #region Internal Classes

    internal static class NativeInterfaces
    {
        #region Public Interfaces

        [ComImport, Guid("42f85136-db7e-439c-85f1-e4075d135fc8"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IFileDialog : IModalWindow
        {
            [PreserveSig]
            new int Show([In] IntPtr parent);

            void SetFileTypes([In] uint cFileTypes, [In][MarshalAs(UnmanagedType.LPArray)] COMDLG_FILTERSPEC[] rgFilterSpec);

            void SetFileTypeIndex([In] uint iFileType);

            void GetFileTypeIndex(out uint piFileType);

            void Advise([In, MarshalAs(UnmanagedType.Interface)] IFileDialogEvents pfde, out uint pdwCookie);

            void Unadvise([In] uint dwCookie);

            void SetOptions([In] FOS fos);

            void GetOptions(out FOS pfos);

            void SetDefaultFolder([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi);

            void SetFolder([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi);

            void GetFolder([MarshalAs(UnmanagedType.Interface)] out IShellItem ppsi);

            void GetCurrentSelection([MarshalAs(UnmanagedType.Interface)] out IShellItem ppsi);

            void SetFileName([In, MarshalAs(UnmanagedType.LPWStr)] string pszName);

            void GetFileName([MarshalAs(UnmanagedType.LPWStr)] out string pszName);

            void SetTitle([In, MarshalAs(UnmanagedType.LPWStr)] string pszTitle);

            void SetOkButtonLabel([In, MarshalAs(UnmanagedType.LPWStr)] string pszText);

            void SetFileNameLabel([In, MarshalAs(UnmanagedType.LPWStr)] string pszLabel);

            void GetResult([MarshalAs(UnmanagedType.Interface)] out IShellItem ppsi);

            void AddPlace([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi, int alignment);

            void SetDefaultExtension([In, MarshalAs(UnmanagedType.LPWStr)] string pszDefaultExtension);

            void Close([MarshalAs(UnmanagedType.Error)] int hr);

            void SetClientGuid([In] ref Guid guid);

            void ClearClientData();

            void SetFilter([MarshalAs(UnmanagedType.Interface)] IntPtr pFilter);
        }

        [ComImport, Guid("973510DB-7D7F-452B-8975-74A85828D354"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IFileDialogEvents
        {
            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), PreserveSig]
            int OnFileOk([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), PreserveSig]
            int OnFolderChanging([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd,
                         [In, MarshalAs(UnmanagedType.Interface)] IShellItem psiFolder);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void OnFolderChange([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void OnSelectionChange([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void OnShareViolation([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd,
                      [In, MarshalAs(UnmanagedType.Interface)] IShellItem psi,
                      out FDE_SHAREVIOLATION_RESPONSE pResponse);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void OnTypeChange([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void OnOverwrite([In, MarshalAs(UnmanagedType.Interface)] IFileDialog pfd,
                     [In, MarshalAs(UnmanagedType.Interface)] IShellItem psi,
                     out FDE_OVERWRITE_RESPONSE pResponse);
        }

        [ComImport, Guid("d57c7288-d4ad-4768-be02-9d969532d960"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IFileOpenDialog : IFileDialog
        {
            void AddPlace([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi, FileDialogCustomPlace fdcp);

            void GetResults([MarshalAs(UnmanagedType.Interface)] out IShellItemArray ppenum);

            void GetSelectedItems([MarshalAs(UnmanagedType.Interface)] out IShellItemArray ppsai);
        }

        [ComImport, Guid("b4db1657-70d7-485e-8e3e-6fcb5a5c1802"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IModalWindow
        {
            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime), PreserveSig]
            uint Show([In] IntPtr parent);
        }

        [ComImport, Guid("43826D1E-E718-42EE-BC55-A1E261C37BFE"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IShellItem
        {
            void BindToHandler([In, MarshalAs(UnmanagedType.Interface)] IntPtr pbc, [In] ref Guid bhid, [In] ref Guid riid, out IntPtr ppv);

            void GetParent([MarshalAs(UnmanagedType.Interface)] out IShellItem ppsi);

            void GetDisplayName([In] SIGDN sigdnName, [MarshalAs(UnmanagedType.LPWStr)] out string ppszName);

            void GetAttributes([In] uint sfgaoMask, out uint psfgaoAttribs);

            void Compare([In, MarshalAs(UnmanagedType.Interface)] IShellItem psi, [In] uint hint, out int piOrder);
        }

        [ComImport, Guid("B63EA76D-1F85-456F-A19C-48159EFA858B"), InterfaceType(ComInterfaceType.InterfaceIsIUnknown)]
        public interface IShellItemArray
        {
            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void BindToHandler([In, MarshalAs(UnmanagedType.Interface)] IntPtr pbc, [In] ref Guid rbhid,
                    [In] ref Guid riid, out IntPtr ppvOut);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void GetPropertyStore([In] int Flags, [In] ref Guid riid, out IntPtr ppv);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void GetPropertyDescriptionList([In] ref PROPERTYKEY keyType, [In] ref Guid riid, out IntPtr ppv);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void GetAttributes([In] SIATTRIBFLAGS dwAttribFlags, [In] uint sfgaoMask, out uint psfgaoAttribs);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void GetCount(out uint pdwNumItems);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void GetItemAt([In] uint dwIndex, [MarshalAs(UnmanagedType.Interface)] out IShellItem ppsi);

            [MethodImpl(MethodImplOptions.InternalCall, MethodCodeType = MethodCodeType.Runtime)]
            void EnumItems([MarshalAs(UnmanagedType.Interface)] out IntPtr ppenumShellItems);
        }

        #endregion Public Interfaces
    }

    [SuppressUnmanagedCodeSecurity]
    internal static class NativeMethods
    {
        #region Public Fields

        public const int ERROR_CANCELLED = unchecked((int)0x800704C7);

        #endregion Public Fields

        #region Public Methods

        [DllImport("user32.dll")]
        public static extern IntPtr GetActiveWindow();

        [DllImport("shell32.dll", SetLastError = true, CharSet = CharSet.Unicode, PreserveSig = false)]
        [return: MarshalAs(UnmanagedType.Interface)]
        public static extern object SHCreateItemFromParsingName(
            [MarshalAs(UnmanagedType.LPWStr)] string pszPath, IBindCtx pbc, ref Guid riid);

        #endregion Public Methods
    }

    #endregion Internal Classes

    #region Private Classes

    [ComImport, Guid("DC1C5A9C-E88A-4dde-A5A1-60F82A20AEF7")]
    private class FileOpenDialog { }

    #endregion Private Classes
}