Edit selected item of datagridview and .txt file as well

if you don't select row, it won't do anything, that might be the problem..you could give a warning message..

private void button2_Click(object sender, EventArgs e)
{
if (dataGridView1.SelectedRows.Count > 0)
{
//delete code here
}
else
{
//MessageBox.Show("no row selected to delete")
}
} 

How do you want to edit? Do you want to use CellValueChanged event? User will doubleclick on a cell, type new value..

 

private void dataGridView1_CellValueChanged(object sender, DataGridViewCellEventArgs e)
{
List myList = File.ReadAllLines("contact.txt").ToList();
string editLine = myList[e.RowIndex].ToString();
string newValue = dataGridView1.Rows[e.RowIndex].Cells[e.ColumnIndex].Value.ToString();
string[] con = editLine.Split(',');
string oldValue = con[e.ColumnIndex].ToString();
myList.RemoveAt(e.RowIndex);
myList.Insert(e.RowIndex, editLine.Replace(oldValue, newValue));
File.WriteAllLines("contact.txt", myList.ToArray());
}