Developer's Notes

public sealed class OUPickerDialog
{
    public OUPickerDialog()
    {
        Caption = "The container picker";
        Title = "Select a container:";
    }

    #region Imports
    // all strings in structure will be marshaled as LPWStr     
    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]     
    private struct DSBrowseInfo
    {
        public int structSize;
        public IntPtr dlgOwner;

        public string dlgCaption;
        public string treeViewTitle;
        public IntPtr rootPath;

        // in/out string must be declared as String in struct/class,          // not as StringBuilder         public string path;
        public int pathSize;

        public int flags;
        public IntPtr callback;
        public IntPtr lParam;
        public int returnFormat;

        public string userName;
        public string password;

        public string objectClass;
        public int objectClassSize;
    };

    [DllImport("dsuiext.dll", CharSet = CharSet.Unicode)]
    private static extern int DsBrowseForContainerW(ref DSBrowseInfo info);

    private const int DSBI_ENTIREDIRECTORY = 0x00090000;
    private const int MAX_PATH = 256;
    #endregion      
    #region Properties
    /// <summary>     
    /// Gets or sets text to display on dialog box caption     
    /// </summary>     
    public string Caption { get; set; }

    /// <summary>     
    /// Gets or sets title displayed above directory tree     
    /// </summary>     
    public string Title { get; set; }

    /// <summary>     
    /// Gets or sets path to start browsing from     
    /// </summary>     
    public string RootPath { get; set; }

    /// <summary>     
    /// Gets path selected by user or empty string if nothing has been selected     
    /// </summary>     
    public string SelectedPath { get; private set; }

    /// <summary>     
    /// Gets name selected by user or empty string if nothing has been selected     
    /// </summary>     
    public string SelectedName { get; private set; }
    #endregion      
    #region Methods
    /// <summary>     
    /// Displays a modal picker dialog and returns OU path as selected by user or empty string if nothing     
    /// has been selected     
    /// </summary>     
    /// <returns><c>true</c> if user selected a unit or <c>false</c> otherwise</returns>     
    public bool? ShowDialog()
    {
        // initialize all members         
        SelectedPath = String.Empty;         
        SelectedName = String.Empty;          
        DSBrowseInfo dsbi = new DSBrowseInfo();

        dsbi.structSize = Marshal.SizeOf(dsbi);
        dsbi.dlgCaption = Caption;
        dsbi.treeViewTitle = Title;
        if (RootPath != null)
            dsbi.rootPath = Marshal.StringToHGlobalAuto(RootPath);

        dsbi.path = new string(new char[MAX_PATH]);
        dsbi.pathSize = MAX_PATH;
        dsbi.flags = DSBI_ENTIREDIRECTORY;

        int status = DsBrowseForContainerW(ref dsbi);

        bool? ret = false;
        if (status == 1)
        {
            ret = true;
            SelectedPath = dsbi.path;
            SelectedName = CalcOUName(SelectedPath);
            RootPath = Marshal.PtrToStringAuto(dsbi.rootPath);
        }
        return ret;
    }

    private static string CalcOUName(string ou)
    {
        int idx = 0;
        do         {             idx = ou.IndexOf(@",", idx + 1);
        } while (idx > 0 && ou[idx - 1] == '\\');
        ou = ou.Substring(0, idx);
        return ou;
    }
    #endregion 
  }