WinForm实现为TextBox设置水印文字功能

2020-01-24 02:30:41

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本文实例展示了WinForm实现为TextBox设置水印文字功能，非常实用的技巧，分享给大家供大家参考。

关键代码如下：

using System;using System.Runtime.InteropServices;using System.Windows.Forms;namespace WinFormUtilHelpV2{  /// <summary>  /// 基于.NET 2.0的TextBox工具类  /// </summary>  public static class TextBoxToolV2  {    private const int EM_SETCUEBANNER = 0x1501;    [DllImport("user32.dll", CharSet = CharSet.Auto)]    private static extern Int32 SendMessage     (IntPtr hWnd, int msg, int wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);    /// <summary>    /// 为TextBox设置水印文字    /// </summary>    /// <param name="textBox">TextBox</param>    /// <param name="watermark">水印文字</param>    public static void SetWatermark(this TextBox textBox, string watermark)    {      SendMessage(textBox.Handle, EM_SETCUEBANNER, 0, watermark);    }    /// <summary>    /// 清除水印文字    /// </summary>    /// <param name="textBox">TextBox</param>    public static void ClearWatermark(this TextBox textBox)    {      SendMessage(textBox.Handle, EM_SETCUEBANNER, 0, string.Empty);    }  }}

测试代码如下：

using System;using System.Windows.Forms;using WinFormUtilHelpV2;namespace WinFormUtilHelpV2Test{  public partial class WinTextBoxToolV2Test : Form  {    public WinTextBoxToolV2Test()    {      InitializeComponent();    }    private void WinTextBoxToolV2Test_Load(object sender, EventArgs e)    {      textBox1.SetWatermark("请输入用户名称....");      textBox2.SetWatermark("请输入用户密码....");    }    private void button1_Click(object sender, EventArgs e)    {      textBox1.ClearWatermark();      textBox2.ClearWatermark();    }  }}

测试效果如下图所示：