c# textbox使用

在C#中，你可以使用TextBox控件的属性来设置提示文字。具体的属性是WatermarkText。

下面是一个示例代码：

using System;
using System.Windows.Forms;

namespace TextBoxWatermarkExample
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
            textBox1.WatermarkText = "请输入文本";
        }
    }

    public class TextBoxWithWatermark : TextBox
    {
        private string watermarkText;

        public TextBoxWithWatermark()
        {
            this.GotFocus += TextBoxWithWatermark_GotFocus;
            this.LostFocus += TextBoxWithWatermark_LostFocus;
        }

        public string WatermarkText
        {
            get { return watermarkText; }
            set
            {
                watermarkText = value;
                this.Text = watermarkText;
                this.ForeColor = SystemColors.GrayText;
            }
        }

        private void TextBoxWithWatermark_GotFocus(object sender, EventArgs e)
        {
            if (this.Text == watermarkText)
            {
                this.Text = "";
                this.ForeColor = SystemColors.WindowText;
            }
        }

        private void TextBoxWithWatermark_LostFocus(object sender, EventArgs e)
        {
            if (string.IsNullOrEmpty(this.Text))
            {
                this.Text = watermarkText;
                this.ForeColor = SystemColors.GrayText;
            }
        }
    }
}

在这个示例中，我们创建了一个自定义的TextBox控件 TextBoxWithWatermark，它具有一个WatermarkText属性。