measuring distance in inches and feets

Try this one:

private void button1_Click(object sender, EventArgs e)
{
   const int divider = 12;
 
   double distance1 = double.Parse(textBox1.Text);
   double distance2 = double.Parse(textBox2.Text);
 
   double totalInches = distance1 + distance2;
   double totalFeet = totalInches / divider;
   MessageBox.Show("Total in inches: " + totalInches.ToString() + "Total in feet: " + totalFeet.ToString());
}

Hope you get the logic from here. Did not included data input validation anymore :)

BTW, input here is fixed for inches you can try converting all input to inches first by creating a function that will return the converted values as inches equivalent.

Regards,
Eduard