WinForm给控件加入hint文字

本文代码主要是参考别人的，仅为个人记录，方面后续使用~

效果图：

主要代码在一个Win32Utility类中，代码如下：

    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;

        //本文地址：http://www.cnblogs.com/Interkey/p/HintText.html

        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();
        }
    }

本文地址：http://www.cnblogs.com/Interkey/p/HintText.html

使用时，如以下代码即可，只不过仅限在少数控件上（主要用在TextBox上，当然也可以用在ComboBox上，不过有限制）

        Win32Utility.SetCueText(this.tb_UserName, "请输入用户名");
        Win32Utility.SetCueText(this.tb_Password, "请输入密码");
        Win32Utility.SetCueText(this.tb_ConfigPassword, "请输入确认密码");
        Win32Utility.SetCueText(this.tb_Email, "请输入邮箱");

        //Win32Utility.SetCueText(this.richTextBox1, "123456");//设置其他控件无效

        //this.comboBox1.DropDownStyle = ComboBoxStyle.DropDownList;//在这种样式下无效
        Win32Utility.SetCueText(this.comboBox1, "请选择");

 以上即可实现效果，不过在此提供了相应代码下载；

 本文参考了以下文章:

C#/WinForm给控件加入hint文字
C# TextBox with Outlook 2007-style prompt