Sum of form entries

Hello!
I'm a beginner C# programmer, I just want to know how would I go around writing a script that adds digit entered in a form?:undecided

 

something like this

Code:

int x = 0;
foreach (char c in textBox1.Text)
{
      x += Convert.ToInt32(c.ToString());
}
 MessageBox.Show(x.ToString());

 

first gotta read welcome to c# then start workin