C#/WinForm给控件加入hint文字

本文转载：http://www.cnblogs.com/qingci/archive/2012/10/15/2724373.html

今天突然来了一个这样的需求，需要在C#的编辑框上加入一个Hint水印效果，类似如下图：

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(); 
        }
 
    }
 

然后在程序里这样调用即可。实现超简单… （本文章无源码，需要使用直接拷贝如上代码即可）

PS:最后推荐一个很强大的，在CodeProject上看到的。

http://www.codeproject.com/Articles/15954/C-TextBox-with-Outlook-2007-style-prompt