Programming a windows form in a mature way
<p>I am very new in C#. I have written a code to get two numbers in two text boxes and basically show their multiplication in a third text box.</p>

<p>The code is like: </p>

<pre><code>private void button1_Click(object sender, EventArgs e)
{
    double A = double.Parse(textBox2.Text); 
    double B = double.Parse(textBox3.Text); //gets the hourly wage
    double C = A * B; 
}
</code></pre>

<p>I have written them all in an executing button class. How can I get "A" and "B" in their own private texbox classes and relate them in "C" text box class?
I need to do it in order to validate the textboxes to give the user an error if he leaves any textboxes empty.</p>
