这个控件其实是 .NET 1.1 新增的一个控件，可以用来浏览文件夹。
对于 1.0 我写过一片文章来介绍如何做这样的一个控件 http://dev.csdn.net/Develop/article/21/article/17/17635.shtm
今天一个同事碰到了一个奇怪的问题，很简单的代码
FolderBrowserDialog dlg=new FolderBrowserDialog();dlg.ShowDialog();
结果 文件夹选择窗体，显示不正确。结果如图所示
这个问题，其实很容易修复。只要把你当前进程的Appartment State 设置为 STA 就可以了，或者给 Main 函数加上一个属性
[STAThread]public static void Main()
{
}
出现这个问题，主要是跟 FolderBrowserDialog 的实现有关系，这个.NET 控件其实是 win32 Shell Ole 控件的一个重新包装，你可以通过reflector看到具体的代码
protected override bool RunDialog(IntPtr hWndOwner){
IntPtr ptr1 = IntPtr.Zero; bool flag1 = false; UnsafeNativeMethods.Shell32.SHGetSpecialFolderLocation(hWndOwner, (int) this.rootFolder, ref ptr1); if (ptr1 == IntPtr.Zero)
{ UnsafeNativeMethods.Shell32.SHGetSpecialFolderLocation(hWndOwner, 0, ref ptr1); if (ptr1 == IntPtr.Zero) { throw new Exception(SR.GetString("FolderBrowserDialogNoRootFolder"));
} } int num1 = 0x40; if (!this.showNewFolderButton) { num1 += 0x200; } Application.OleRequired(); IntPtr ptr2 = IntPtr.Zero; try { UnsafeNativeMethods.BROWSEINFO browseinfo1 = new UnsafeNativeMethods.BROWSEINFO(); IntPtr ptr3 = Marshal.AllocHGlobal((int) (260 * Marshal.SystemDefaultCharSize)); IntPtr ptr4 = Marshal.AllocHGlobal((int) (260 * Marshal.SystemDefaultCharSize)); UnsafeNativeMethods.BrowseCallbackProc proc1 = new UnsafeNativeMethods.BrowseCallbackProc(this.FolderBrowserDialog_BrowseCallbackProc); browseinfo1.pidlRoot = ptr1; browseinfo1.hwndOwner = hWndOwner; browseinfo1.pszDisplayName = ptr3; browseinfo1.lpszTitle = this.descriptionText; browseinfo1.ulFlags = num1; browseinfo1.lpfn = proc1; browseinfo1.lParam = IntPtr.Zero; browseinfo1.iImage = 0; ptr2 = UnsafeNativeMethods.Shell32.SHBrowseForFolder(browseinfo1); if (ptr2 != IntPtr.Zero) { UnsafeNativeMethods.Shell32.SHGetPathFromIDList(ptr2, ptr4); this.selectedPathNeedsCheck = true; this.selectedPath = Marshal.PtrToStringAuto(ptr4); Marshal.FreeHGlobal(ptr4); Marshal.FreeHGlobal(ptr3); flag1 = true; } } finally { UnsafeNativeMethods.IMalloc malloc1 = FolderBrowserDialog.GetSHMalloc(); malloc1.Free(ptr1); if (ptr2 != IntPtr.Zero) { malloc1.Free(ptr2); } } return flag1;}
而shell32 的申明如下：
[SuppressUnmanagedCodeSecurity, ComVisible(false)]internal class Shell32{ // Methods public Shell32(); [DllImport("shell32.dll", CharSet=CharSet.Auto)] public static extern IntPtr SHBrowseForFolder([In] UnsafeNativeMethods.BROWSEINFO lpbi); [DllImport("shell32.dll")] public static extern int SHGetMalloc([Out, MarshalAs(UnmanagedType.LPArray)] UnsafeNativeMethods.IMalloc[] ppMalloc); [DllImport("shell32.dll", CharSet=CharSet.Auto)] public static extern bool SHGetPathFromIDList(IntPtr pidl, IntPtr pszPath); [DllImport("shell32.dll")] public static extern int SHGetSpecialFolderLocation(IntPtr hwnd, int csidl, ref IntPtr ppidl);}