创建 C# 表单对象时出现 System.StackOverflowException

有两种形式，一类。从主窗体我打开第二个：

private void button1_Click(object sender, EventArgs e)
        {
            Form2 form2 = new Form2();
            this.Hide();
            form2.ShowDialog();
            this.Close();
        }

在另一个类中，我还为第二种形式创建了一个对象

Form2 form2 = new Form2();

并且在这一行上它会抛出一个异常 System.StackOverflowException。我没有在第二个表单上创建对象。你怎么能解决这个问题？毕竟我需要通过这个类的方法来改变第二个窗体上的组件。这是整个代码：

 public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            Form2 form2 = new Form2();
            this.Hide();
            form2.ShowDialog();
            this.Close();
        }
    }

public partial class Form2 : Form
    {
        Ans ans = new Ans();
        private int index = -1;

        public Form2()
        {
            InitializeComponent();
            ans.Test(radioButton1, radioButton2);

            Shown += Form1_Shown15;
        }

        private void radioButton_Click(object sender, EventArgs e)
        {
            RadioButton button = sender as RadioButton;

            if (button == radioButton1) { index = 0; }
            if (button == radioButton2) { index = 1; }
        }

        private async void Form1_Shown25(object sender, EventArgs e)
        {
            verticalProgressBar1.Value = 100;
            for (int i = 25 * 60; i > 0; i--)
            {
                verticalProgressBar1.Value = i * 100 / (25 * 60);
                await Task.Delay(1000);
            }
            Close();
        }

        private void button3_Click(object sender, EventArgs e)
        {
            try
            {
                ans.Correct(index);

                radioButton1.Checked = false;
                radioButton2.Checked = false;

                index = -1;
            }
            catch { return; }

            ans.Index++;

            if (ans.Index > 47)
            {
                MessageBox.Show();
                return;
            }
            ans.Test(radioButton1, radioButton2);
        }
    }
public class Ans
{
 Form2 form2 = new Form2();

        private List<string> test = new List<string>()
        { };

        private bool[,] boolTest =
        { };

        public int correct = 0;

        public int TestIndex { get; set; }
        public int Index { get; set; }

        public string GetCorrect { get; set; }

        public void Test(Control control1, Control control2)
        {
            control1.Text = test[TestIndex];
            TestIndex++;
            control2.Text = test[TestIndex];
            TestIndex++;
        }

        public void Correct(int i)
        {
            SystemSounds.Exclamation.Play();
            #region 1-10
            //1
            if (Index == 0)
            {
                if (boolTest[0, i] == true)
                {
                    form2.pictureBox2.BackColor = Color.Green;
                    form2.label2.Text = "";
                    correct++;
                    return;
                }
                else
                {
                    form2.pictureBox2.BackColor = Color.Red;
                    form2.label2.BackColor = Color.Red;
                }
            }           
        }
    }