You will need to add code that will execute on the SelectedIndexChanged event of each combo;
(Example below is a form with 2 combobox, drop down list style, and a label, and is basically your basic times table multiplier
e.g.
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void Form1_Load(object sender, EventArgs e)
{
for (int x = 0; x < 11; x++)
{
comboIP1.Items.Add(x.ToString());
comboIP2.Items.Add(x.ToString());
}
}
private void calcResult(object sender, EventArgs e)
{
try
{
int input1 = int.Parse(comboIP1.SelectedItem.ToString());
int input2 = int.Parse(comboIP2.SelectedItem.ToString());
int result = input1 * input2;
labelResult.Text = result.ToString();
}
catch (Exception ex)
{
labelResult.Text = "0";
}
}
}