用于在单击时清除文本框的C#代码不起作用，错误

using System;
using System.Windows.Forms;

public class MainForm : Form
{
    private TextBox textBox;
    private Button clearButton;

    public MainForm()
    {
        // 初始化文本框
        textBox = new TextBox();
        textBox.Location = new System.Drawing.Point(20, 20);
        textBox.Size = new System.Drawing.Size(200, 20);

        // 初始化按钮
        clearButton = new Button();
        clearButton.Text = "Clear";
        clearButton.Location = new System.Drawing.Point(20, 50);
        clearButton.Click += ClearButton_Click; // 绑定事件处理程序

        // 将控件添加到窗体
        this.Controls.Add(textBox);
        this.Controls.Add(clearButton);

        // 设置窗体属性
        this.ClientSize = new System.Drawing.Size(280, 100);
        this.Text = "Clear TextBox Example";
    }

    private void ClearButton_Click(object sender, EventArgs e)
    {
        textBox.Clear(); // 清除文本框内容
    }

    [STAThread]
    static void Main()
    {
        Application.EnableVisualStyles();
        Application.SetCompatibleTextRenderingDefault(false);
        Application.Run(new MainForm());
    }
}