How to show all results and not just one in a delegate calculator
<p>I just got the task to create a WPF application that shows the results for different calculations (+,-,/,%,etc.) by using a delegate (public delegate 
void Calculation(int a, int b). 
The problem is that my program only seems to show the last result of those calculations but I need to show them all in a listbox. </p>

<p>This is my code right now:</p>

<pre><code>public partial class MainWindow : Window
{
      public delegate string CalculateHandler(int a, int b);
      public MainWindow()
      {
           InitializeComponent();
      }

      private void BtnCalculate_Click(object sender, RoutedEventArgs e) { 

        CalculateHandler Calculate = new CalculateHandler(Add.Addition);
        Calculate += Subtract.Subtraction;
        Calculate += Multi.Multiplication;
        Calculate += Div.Division;
        Calculate += Root.Ro;
        Calculate += Mod.Modulo;
        Calculate += Pot.Potency;

        int a = Int32.Parse(TextBoxZahlA.Text); 
        int b = Int32.Parse(TextBoxZahlB.Text);

        listBox.Items.Add(Calculate(a, b));
        listBox.Items.Refresh(); 
    }
}
</code></pre>

<p>Example for one of the calculations:</p>

<pre><code>class Multi
{
    public static string Multiplication (int a, int b)
        {
            string result3 = a + " * " + b + " = " + (a * b);
            return result3;
        }
    }
}
</code></pre>

<p>Thanks for any sort of help!!</p>