V-T-S Rechner 2.0

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication1
{
    public partial class Fenster : Form
    {
        public Fenster()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {

            if (vBox.Text == "")
            {
                double s = Convert.ToDouble(sBox.Text);
                double t = Convert.ToDouble(tBox.Text);
                double ergebnis = 0;
                ergebnis = s / t;
                vBox.Text = Convert.ToString(ergebnis);
            }

            else if (sBox.Text == "")
            {
                double v = Convert.ToDouble(vBox.Text);
                double t = Convert.ToDouble(tBox.Text);
                double ergebnis = 0;
                ergebnis = v * t;
                sBox.Text = Convert.ToString(ergebnis);
            }
            else if (tBox.Text == "")
            {
                double v = Convert.ToDouble(vBox.Text);
                double s = Convert.ToDouble(sBox.Text);
                double ergebnis = 0;
                ergebnis = s / v;
                tBox.Text = Convert.ToString(ergebnis);
            }
            else
            {
                MessageBox.Show("Geben sie mindestens 2 Werte ein", "Fehler", MessageBoxButtons.OK, MessageBoxIcon.Error, MessageBoxDefaultButton.Button1);
            }

        }





        private void vBox_Enter(object sender, EventArgs e)
        {
            if (vBox.Text != "" && sBox.Text != "" && tBox.Text != "")
            {
                vBox.Text = "";
                sBox.Text = "";
                tBox.Text = "";
            }
        }

        private void sBox_Enter(object sender, EventArgs e)
        {
            if (vBox.Text != "" && sBox.Text != "" && tBox.Text != "")
            {
                vBox.Text = "";
                sBox.Text = "";
                tBox.Text = "";
            }
        }

        private void tBox_Enter(object sender, EventArgs e)
        {
            if (vBox.Text != "" && sBox.Text != "" && tBox.Text != "")
            {
                vBox.Text = "";
                sBox.Text = "";
                tBox.Text = "";
            }
        }



    }
}