programming in C# : System calculates installments and due dates With Source code

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

namespace System_calculate_installments

{

    public partial class Form2 : Form

    {

        public Form2()

        {

            InitializeComponent();

        }

        DataTable dt = new DataTable();

        private void Form2_Load(object sender, EventArgs e)

        {

            dt.Columns.Add("Installment", typeof(string));

            dt.Columns.Add("Value", typeof(double));

            dt.Columns.Add("Due_date", typeof(DateTime));

            dataGridView1.DataSource = dt;

        }

        private void button1_Click(object sender, EventArgs e)

        {

            double price_v, adv_payment, installment_value, n_installments,final_installment;

            price_v = double.Parse(textBox1.Text);

            adv_payment = double.Parse(textBox2.Text);

            installment_value = double.Parse(textBox3.Text);

            n_installments = Math.Ceiling((price_v - adv_payment) / installment_value);

            final_installment = (price_v - adv_payment) % installment_value;

            dataGridView1.DataSource = null;

            dt.Clear();

            dataGridView1.DataSource = dt;

            for (int i = 1; i <= n_installments; i++)

            {

                var date_payment = (DateTime.Today.AddMonths(i)).ToString("MM-dd-yyyy");

                dt.Rows.Add("Installment" + i, textBox3.Text, date_payment);

            }

            if (final_installment != 0)

            {

                int lastrow = dataGridView1.Rows.Count - 1;

                dataGridView1.Rows[lastrow].Cells[1].Value = final_installment;

            }

        }

          

    }

}