索引超出了数组界限问题。

namespace _0ne
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();//窗口初始化
        }

        private void button1_Click(object sender, EventArgs e)
        {
            string[,] str = new string[2, 3];
            StreamReader sr = File.OpenText("C:\\Users\\Administrator\\Desktop\\myy.txt");
            int k = 0;//当前读取的是第几行
            while (sr.Peek() != -1)
            {
                str[k % 2, k % 2] = sr.ReadLine();
                k++;
            }
            for (int i = 1; i <=3; i++)
            {
                string controlName1 = string.Format("textBox1{0}", i);
                string controlName2 = string.Format("textBox1{0}", i);
                (Controls.Find(controlName1, false)[0]).Text = str[0, i-1];/////为什么这里总是报出索引超出了数组界限。？？？这是为什么
                (Controls.Find(controlName2, false)[0]).Text = str[1, i-1];
            }
            sr.Close();
        }