C#/WinForm给控件加入hint文字

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：

以前在手机上(wp)上做过类似的效果。参考silverlight toolkit 的searchTextBox。现在要在winform下制作，开始我还以为应该有啥啥属性可以一键搞定，结果目测了一下,没有什么属性，于是乎百度了一下，网上说用win32API来做，这倒挺神奇的,参考别人做了如下列子。

申明一个Win32Utility类,静态的,

代码如下

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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();
        }

    }

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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）

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另外一直想研究一下Win32API，不知道谁有没有好的资料推荐一下。

做了这么久程序猿对系统的内核还是未入门阶段,真心惭愧！！！

大侠们有资料就推荐一下哦, 3Q

本人从事网站开发，WP/Win8开发。目前想和一些有志向的朋友一同研究

一下WP/Win8这些新事物，一起玩转论坛,一起合作出软件,一起学习,一起赚Money.

有意向者联系QQ：61797528

海内存知己，天涯若比邻！

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