c#中的文本框解析

我有问题解析从textBox在c#。基本上，我试图设置一些值为整数，之后，当人类型的数字在文本框中，如果它是相同的增加计数器。但我必须解析int到字符串，这里我失败了。

代码如下:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
namespace kontrolno {
  public partial class Form1: Form {
    int counter;
    int A = 13;
    int B = 2116;
    public Form1() {
      InitializeComponent();
    }
    private void button1_Click(object sender, EventArgs e) {
      label3.Text = counter.ToString();
    }
    private void label3_Click(object sender, EventArgs e) {}
    private void groupBox1_Enter(object sender, EventArgs e) {}
    private void textBox1_TextChanged(object sender, EventArgs e) {
      int A = Int32.Parse(textBox1.Text);
      if (textBox1.Text = A) /*As you see somewhere here i have a problem*/
    }
    private void textBox2_TextChanged(object sender, EventArgs e) {
      /*Here must be parsed second textBox*/
    }
    private void comboBox1_SelectedIndexChanged(object sender, EventArgs e) {
      switch (comboBox1.SelectedIndex) //comboBox 1st case
      {
      case 0:
        button1.Enabled = false;
        textBox1.Text = "13";
        textBox2.Text = "2116";
        radioButton1.Checked = true;
        checkBox1.Checked = true;
        /*Those 3 answers should 
        checkBox2.Checked = true;   be counted as one 
        checkBox4.Checked = true;  when mark is formed*/
        checkBox5.Checked = true;
        break;
      case 1:
        /*comboBox 2nd case*/
        button1.Enabled = true;
        textBox1.Text = "";
        textBox2.Text = "";
        radioButton1.Checked = false;
        checkBox1.Checked = false;
        checkBox2.Checked = false;
        checkBox4.Checked = false;
        checkBox5.Checked = false;
        break;
      }
    }
    private void radioButton1_CheckedChanged(object sender, EventArgs e) {
      if (radioButton1.Checked) {
        counter++;
      }
    }
    private void checkBox1_CheckedChanged(object sender, EventArgs e) {
      if (checkBox1.Checked) {
        counter++;
      }
    }
    private void checkBox2_CheckedChanged(object sender, EventArgs e) {
      if (checkBox2.Checked) {
        counter++;
      }
    }
    private void checkBox4_CheckedChanged(object sender, EventArgs e) {
      if (checkBox4.Checked) {
        counter++;
      } else {
        counter--;
      }
    }
    private void checkBox5_CheckedChanged(object sender, EventArgs e) {
      if (checkBox5.Checked) {
        counter++;
      } else {
        counter--;
      }
    }
  }
}

所以我有问题，但我不知道如何解决它。该代码的思想是要测试的。组合框有2个项目在第一项练习用户看到所有的问题和答案。在第二项中，用户填写答案，当按下按钮时，他收到他的分数。我还没有实现标记公式，因为不能从文本框得到结果。

我还想问是否有可能从复选框中得到3个答案算作一个?

应该很简单，但是我刚刚崩溃了，无法解决这个问题。