Átlagsebesség - Windows Form Application

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 atlagsebesseg
{
    public partial class Form1 : Form
    {
        double time, speed, distance, meter, sec, mets;

        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            if (v.Text == "" && s.Text != "" && t.Text != "")
            {
                v.Text = Convert.ToString(Convert.ToInt32(s.Text) / Convert.ToInt32(t.Text));
            }
            if (t.Text.Length == 0 && s.Text.Length != 0 && v.Text.Length != 0)
            {
                t.Text = Convert.ToString(Convert.ToInt32(s.Text) / Convert.ToInt32(v.Text));
            }
            if (s.Text.Length == 0 && v.Text.Length != 0 && t.Text.Length != 0)
            {
                s.Text = Convert.ToString(Convert.ToInt32(t.Text) * Convert.ToInt32(v.Text));
            }
            //if (s.Text == "" && v.Text == "" || s.Text == "" && t.Text == "" || v.Text == "" && t.Text == "")
            //{
            //    MessageBox.Show("Minimum 2 mezőt ki kell tölteni!");
            //}

            try
            {
                distance = Convert.ToDouble(v.Text);
                time = Convert.ToInt32(t.Text);
                speed = Convert.ToInt32(s.Text);
            }
            catch (FormatException)
            {
                MessageBox.Show("Minimum 2 mezőt ki kell tölteni!");
            }

            meter = (speed / time) / 1000;
            sec = (speed / distance) * 3600;
            mets = (distance * time) * 0.27777777777778;

            label6.Text = Convert.ToString(meter)+" m";
            label8.Text = Convert.ToString(sec)+" s";
            label10.Text = Convert.ToString(mets)+" m/s";
        }

        private void button2_Click(object sender, EventArgs e)
        {
            v.Text = s.Text = t.Text = "";
            label6.Text = " m";
            label8.Text = " s";
            label10.Text = " m/s";
        }

        private void button3_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}