int elma = Convert.ToInt32(textBox1.Text);
            int armut = Convert.ToInt32(textBox2.Text);
            int portakal = Convert.ToInt32(textBox3.Text);
           int limon = Convert.ToInt32(textBox4.Text);
            label12.Text = (elma * 20).ToString();
            label13.Text = (armut * 30).ToString();
            label14.Text = (portakal * 15).ToString();
            label15.Text = (limon * 25).ToString();
            double toplam = Convert.ToDouble(label12.Text + label13.Text + label14.Text + label15.Text);
            label17.Text = (toplam).ToString();
            
            

        }