如何在C#中以编程方式更改文本字段？

using System;
using System.Windows.Forms;

namespace WindowsFormsApp
{
    public partial class Form1 : Form
    {
        private TextBox textBox;

        public Form1()
        {
            InitializeComponent();
            InitializeTextBox();
        }

        private void InitializeTextBox()
        {
            textBox = new TextBox();
            textBox.Location = new System.Drawing.Point(100, 100);
            textBox.Size = new System.Drawing.Size(200, 20);
            textBox.Text = "初始文本";
            this.Controls.Add(textBox);
        }

        private void button1_Click(object sender, EventArgs e)
        {
            textBox.Text = "新的文本值";
        }
    }
}