If you use the keyword params before an array parameter used as the last parameter to a method, then the calling code can pass any number of values for that parameter. The following code defines a ShowValues method that can take any number of string parameters.

// Display zero or more values.
private void ShowValues(params string[] values)
{
    lstValues.Items.Clear();
    foreach (string value in values)
    {
        lstValues.Items.Add(value);
    }
}

The following code shows how the example program calls ShowValues passing it 0, 3, or 5 parameters.

private void btn0_Click(object sender, EventArgs e)
{
    ShowValues();
}

private void btn3_Click(object sender, EventArgs e)
{
    ShowValues("Red", "Green", "Blue");
}

private void btn5_Click(object sender, EventArgs e)
{
    ShowValues("Aardvark", "Bear", "Cantalope", "Dingo", "Eagle");
}