Win32 TreeView function (SysTreeView32)

public class TreeView
            {
                //http://www.perlmonks.org/bare/?node_id=478016
                //https://stackoverflow.com/questions/3660556/how-to-select-an-item-in-a-treeview-using-win32-api
                //https://bytes.com/topic/c-sharp/answers/621199-tvm_getitem-does-not-return-unicode-label

                //Define TreeView Flags and Messages
                private const int BN_CLICKED = 0xF5;
                private const int TV_FIRST = 0x1100;
                private const int TVGN_ROOT = 0x0;
                private const int TVGN_NEXT = 0x1;
                private const int TVGN_CHILD = 0x4;
                private const int TVGN_FIRSTVISIBLE = 0x5;
                private const int TVGN_NEXTVISIBLE = 0x6;
                private const int TVGN_CARET = 0x9;
                private const int TVM_SELECTITEM = (TV_FIRST + 11);
                private const int TVM_GETNEXTITEM = (TV_FIRST + 10);
                private const int TVM_GETITEM = (TV_FIRST + 12);
                private const int TVIF_TEXT = 0x1;
                private const int MY_MAXLVITEMTEXT = 128;

                [DllImport("user32", EntryPoint = "SendMessageW")]
                private static extern int SendMessageTVI(IntPtr hWnd, int wMsg, int wParam, ref TVITEM tvi);

                [DllImport("kernel32.dll")]
                public static extern IntPtr LocalAlloc(uint flags, uint cb);

                [DllImport("kernel32.dll")]
                public static extern IntPtr LocalFree(IntPtr p);

                struct TVITEM
                {
                    public uint mask;
                    public IntPtr hItem;
                    public uint state;
                    public uint stateMask;
                    public IntPtr pszText;
                    public int cchTextMax;
                    public int iImage;
                    public int iSelectedImage;
                    public int cChildren;
                    public IntPtr lParam;
                }

                [DllImport("user32.dll", CharSet = CharSet.Auto)]
                public static extern int SendMessage(int hWnd, int msg, int wParam, IntPtr lParam);
                public static IntPtr GetRoot(IntPtr treeViewHwnd)
                {
                    return new IntPtr(SendMessage((int)treeViewHwnd, TVM_GETNEXTITEM, TVGN_ROOT, IntPtr.Zero));
                }
                public static IntPtr GetNextItem(IntPtr treeViewHwnd, IntPtr lastItem)
                {
                    return new IntPtr(SendMessage((int)treeViewHwnd, TVM_GETNEXTITEM, TVGN_NEXT, lastItem));
                }
                public static IntPtr GetChildItem(IntPtr treeViewHwnd, IntPtr parrentItem)
                {
                    return new IntPtr(SendMessage((int)treeViewHwnd, TVM_GETNEXTITEM, TVGN_CHILD, parrentItem));
                }
                public static void SelectItem(IntPtr treeViewHwnd, IntPtr item)
                {
                    SendMessage((int)treeViewHwnd, TVM_SELECTITEM, TVGN_CARET, item);
                }
                public static IntPtr GetSelectedItem(IntPtr treeViewHwnd)
                {
                    return new IntPtr(SendMessage((int)treeViewHwnd, TVM_GETITEM, TVGN_CARET, IntPtr.Zero));
                }

                public static string GetTreeItemText(IntPtr treeViewHwnd, IntPtr hItem)
                {
                    int ret;
                    TVITEM tvi = new TVITEM();
                    IntPtr pszText = LocalAlloc(0x40, MY_MAXLVITEMTEXT);

                    tvi.mask = TVIF_TEXT;
                    tvi.hItem = hItem;
                    tvi.cchTextMax = MY_MAXLVITEMTEXT;
                    tvi.pszText = pszText;

                    ret = SendMessageTVI(treeViewHwnd, TVM_GETITEM, 0, ref tvi);
                    string buffer = Marshal.PtrToStringUni((IntPtr)tvi.pszText,
                    MY_MAXLVITEMTEXT);

                    //char[] arr = buffer.ToCharArray(); //<== use this array to look at the bytes
//in debug mode

LocalFree(pszText);
                    return buffer;
                }

            }