Get the value from DataGridView to TextBox on c#. TextBox event in DataGridView in c#.

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 GirdViewTextBoxEvent

{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
private void dataGridView1_EditingControlShowing(object sender, DataGridViewEditingControlShowingEventArgs e)
{
var txtBox = e.Control as TextBox;
if (txtBox != null)
{
txtBox.Leave += new EventHandler(txtBox_Leave);
}
}
void txtBox_Leave(object sender, EventArgs e)
{
 try
{
for (int i = 0; i < dataGridView1.Rows.Count; i++)
{
int a = 0, b = 0, c = 0;
a = Convert.ToInt32(dataGridView1.Rows[i].Cells["txtRate"].Value);
b = Convert.ToInt32(dataGridView1.Rows[i].Cells["txtQuantity"].Value);
c = a * b;
dataGridView1.Rows[i].Cells["txtTotal"].Value = c;
}
}
catch (Exception ex)
{
MessageBox.Show(ex.Message.ToString());
}
}
}
}