C#笔记（5）textbox的hint属性

新建类

    public static class Win32Utility    {        [DllImport("user32.dll", CharSet = CharSet.Auto)]        private static extern Int32 SendMessage(IntPtr hWnd, int msg,            int wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);        [DllImport("user32.dll")]        private static extern bool SendMessage(IntPtr hwnd, int msg, int wParam, StringBuilder lParam);        [DllImport("user32.dll")]        private static extern bool GetComboBoxInfo(IntPtr hwnd, ref COMBOBOXINFO pcbi);        [StructLayout(LayoutKind.Sequential)]        private struct COMBOBOXINFO        {            public int cbSize;            public RECT rcItem;            public RECT rcButton;            public IntPtr stateButton;            public IntPtr hwndCombo;            public IntPtr hwndItem;            public IntPtr hwndList;        }        [StructLayout(LayoutKind.Sequential)]        private struct RECT        {            public int left;            public int top;            public int right;            public int bottom;        }        private const int EM_SETCUEBANNER = 0x1501;        private const int EM_GETCUEBANNER = 0x1502;        public static void SetCueText(Control control, string text)        {            if (control is ComboBox)            {                COMBOBOXINFO info = GetComboBoxInfo(control);                SendMessage(info.hwndItem, EM_SETCUEBANNER, 0, text);            }            else            {                SendMessage(control.Handle, EM_SETCUEBANNER, 0, text);            }        }        private static COMBOBOXINFO GetComboBoxInfo(Control control)        {            COMBOBOXINFO info = new COMBOBOXINFO();            //a combobox is made up of three controls, a button, a list and textbox;             //we want the textbox             info.cbSize = Marshal.SizeOf(info);            GetComboBoxInfo(control.Handle, ref info);            return info;        }        public static string GetCueText(Control control)        {            StringBuilder builder = new StringBuilder();            if (control is ComboBox)            {                COMBOBOXINFO info = new COMBOBOXINFO();                //a combobox is made up of two controls, a list and textbox;                 //we want the textbox                 info.cbSize = Marshal.SizeOf(info);                GetComboBoxInfo(control.Handle, ref info);                SendMessage(info.hwndItem, EM_GETCUEBANNER, 0, builder);            }            else            {                SendMessage(control.Handle, EM_GETCUEBANNER, 0, builder);            }            return builder.ToString();        }    }

2.使用

Win32Utility.SetCueText(textBox_username, "用户名");Win32Utility.SetCueText(textBox_password, "密码");