C# FolderBrowserDialog Scroll to Selected Path 文件夹选择框初始位置没有滚动到默认文件夹

            public
            static
            class
             FolderBrowserLauncher
    {
        
            ///
            <summary>
            ///
             Using title text to look for the top level dialog window is fragile.
        
            ///
             In particular, this will fail in non-English applications.
        
            ///
            </summary>
            const
            string _topLevelSearchString = "Browse For Folder";

        ///<summary>/// These should be more robust.  We find the correct child controls in the dialog
        /// by using the GetDlgItem method, rather than the FindWindow(Ex) method,
        /// because the dialog item IDs should be constant.
        ///</summary>constint _dlgItemBrowseControl = 0;
        constint _dlgItemTreeView = 100;

        [DllImport("user32.dll", SetLastError = true)]
        staticextern IntPtr FindWindow(string lpClassName, string lpWindowName);

        [DllImport("user32.dll")]
        staticextern IntPtr GetDlgItem(IntPtr hDlg, int nIDDlgItem);

        [DllImport("user32.dll", CharSet = CharSet.Auto)]
        staticextern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

        ///<summary>/// Some of the messages that the Tree View control will respond to
        ///</summary>privateconstint TV_FIRST = 0x1100;
        privateconstint TVM_SELECTITEM = (TV_FIRST + 11);
        privateconstint TVM_GETNEXTITEM = (TV_FIRST + 10);
        privateconstint TVM_GETITEM = (TV_FIRST + 12);
        privateconstint TVM_ENSUREVISIBLE = (TV_FIRST + 20);

        ///<summary>/// Constants used to identity specific items in the Tree View control
        ///</summary>privateconstint TVGN_ROOT = 0x0;
        privateconstint TVGN_NEXT = 0x1;
        privateconstint TVGN_CHILD = 0x4;
        privateconstint TVGN_FIRSTVISIBLE = 0x5;
        privateconstint TVGN_NEXTVISIBLE = 0x6;
        privateconstint TVGN_CARET = 0x9;


        ///<summary>/// Calling this method is identical to calling the ShowDialog method of the provided
        /// FolderBrowserDialog, except that an attempt will be made to scroll the Tree View
        /// to make the currently selected folder visible in the dialog window.
        ///</summary>///<param name="dlg"></param>///<param name="parent"></param>///<returns></returns>publicstatic DialogResult ShowFolderBrowser(FolderBrowserDialog dlg, IWin32Window parent = null)
        {
            DialogResult result = DialogResult.Cancel;
            int retries = 10;

            using (Timer t = new Timer())
            {
                t.Tick += (s, a) =>
                {
                    if (retries > 0)
                    {
                        --retries;
                        IntPtr hwndDlg = FindWindow((string)null, _topLevelSearchString);
                        if (hwndDlg != IntPtr.Zero)
                        {
                            IntPtr hwndFolderCtrl = GetDlgItem(hwndDlg, _dlgItemBrowseControl);
                            if (hwndFolderCtrl != IntPtr.Zero)
                            {
                                IntPtr hwndTV = GetDlgItem(hwndFolderCtrl, _dlgItemTreeView);

                                if (hwndTV != IntPtr.Zero)
                                {
                                    IntPtr item = SendMessage(hwndTV, (uint)TVM_GETNEXTITEM, new IntPtr(TVGN_CARET), IntPtr.Zero);
                                    if (item != IntPtr.Zero)
                                    {
                                        SendMessage(hwndTV, TVM_ENSUREVISIBLE, IntPtr.Zero, item);
                                        retries = 0;
                                        t.Stop();
                                    }
                                }
                            }
                        }
                    }

                    else
                    {
                        ////  We failed to find the Tree View control.
                        ////  As a fall back (and this is an UberUgly hack), we will send
                        //  some fake keystrokes to the application in an attempt to force
                        //  the Tree View to scroll to the selected item.
                        //
                        t.Stop();
                        SendKeys.Send("{TAB}{TAB}{DOWN}{DOWN}{UP}{UP}");
                    }
                };

                t.Interval = 10;
                t.Start();

                result = dlg.ShowDialog(parent);
            }

            return result;
        }
    }