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
{
///
/// 基于.NET 2.0的TextBox工具类
///
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);
///
/// 为TextBox设置水印文字
///
/// TextBox
/// 水印文字
public static void SetWatermark(this TextBox textBox, string watermark)
{
SendMessage(textBox.Handle, EM_SETCUEBANNER, 0, watermark);
}
///
/// 清除水印文字
///
/// TextBox
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：
希望本文所述的为TextBox设置水印文字功能示例对大家C#程序设计有所帮助！