title: can perform some operations but not all on c# calculator?
body: <p>So far, my addition and subtraction work. But, my multiplication and division do not. This is because the first two numbers I put in get added and them the operation is done. Such as, if 9 * 9 + 3 should be 84, it is 21 on my calculator. That is because it is taking 9+9 + 3; as it only sees the last operator. 
  I have absolutely no idea how to fix this. Is there any helpful insight?</p>
  
  <pre><code>public partial class Form1 : Form
  {
      double num2;
      double num1;
      string c;
  
      public Form1()
      {
          InitializeComponent();
      }
  
      private void btn0_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn0.Text;
      }
  
      private void btn1_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn1.Text;
      }
  
      private void btn2_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn2.Text;
      }
  
      private void btn3_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn3.Text;
      }
  
      private void btn4_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn4.Text;
      }
  
      private void btn5_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn5.Text;
      }
  
      private void btn6_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn6.Text;
      }
  
      private void btn7_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn7.Text;
      }
  
      private void btn8_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn8.Text;
      }
  
      private void btn9_Click(object sender, EventArgs e)
      {
          txtBox.Text = txtBox.Text + btn9.Text;
      }
  
      private void btnDecimal_Click(object sender, EventArgs e)
      {
          if (!txtBox.Text.Contains('.'))
              txtBox.Text += '.';
      }
  
      private void btnClear_Click(object sender, EventArgs e)
      {
          txtBox.Clear();
      }
  
      private void btnAddition_Click(object sender, EventArgs e)
      {
          num1 = num1 + double.Parse(txtBox.Text);
          c = "+";
          txtBox.Clear();
      }
  
      private void btnSubtraction_Click(object sender, EventArgs e)
      {
          num1 = num1 + double.Parse(txtBox.Text);
          c = "-";
          txtBox.Clear();
      }
  
      private void btnMultiplication_Click(object sender, EventArgs e)
      {
          num1 = num1 + double.Parse(txtBox.Text);
          c = "*";
          txtBox.Clear();
      }
  
      private void btnDivision_Click(object sender, EventArgs e)
      {
          num1 = num1 + double.Parse(txtBox.Text);
          c = "/";
          txtBox.Clear();
      }
      private void btnEquals_Click(object sender, EventArgs e)
      {
  
          double result;
  
          num2 = double.Parse(txtBox.Text);
  
          switch (c)
          {
              case "+":
                  result = num1 + num2;
                  txtBox.Text = result.ToString();
                  num1 = 0;
                  break;
              case "-":
                  result = num1 - num2;
                  txtBox.Text = result.ToString();
                  num1 = 0;
                  break;
              case "*":
                  result = num1 * num2;
                  txtBox.Text = result.ToString();
                  num1 = 0;
                  break;
              case "/":
                  if (num2 != 0)
              {
                  result = num1 / num2;
                  txtBox.Text = result.ToString();
              }
              else
              {
                  txtBox.Text = "You can't divide by zero... sign up for Math 100 please =)";
              }
              break;
              default:
                  result = 0;
                  break;
          }
  
      }
  }
  </code></pre>
  
  <p>}</p>