There is no row at position zero..

con.Open();

            SqlDataAdapter da = new SqlDataAdapter();
            da.SelectCommand = new SqlCommand("select * from mytable where ID=" + Convert.ToInt32(textBox3.Text.ToString()), con);

            DataTable dt = new DataTable();
            da.Fill(dt);


// Till now all is working well ...
            dataGridView1.DataSource = dt.DefaultView;


// Here i got the exception :(


dt.Rows[0].BeginEdit();

            dt.Rows[0][0] = Convert.ToInt32(textBox3.Text.ToString());
            dt.Rows[0][1] = textBox4.Text.ToString();

            dt.Rows[0].EndEdit();

            SqlCommandBuilder cb = new SqlCommandBuilder(da);


            da.Update(dt);

            con.Close();