Format de la chaîne d'entrée

private void CalculatePrice()
        {
            try
            {

                txtTVA.Text = (double.Parse(txtPrice.Text) * 0.16).ToString();
                double price = Convert.ToDouble(txtPrice.Text);
                double tva = Convert.ToDouble(txtTVA.Text);
                double total = price + tva;
                txtPriceTVA.Text = Convert.ToString(total);

               
                double.Parse(txtTVA.Text).ToString("#,##0.00");
                double.Parse(txtPriceTVA.Text).ToString("#,##0.00");
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
                //txtPrice.Text = "0";
            }
        }

        private void txtPrice_TextChanged_1(object sender, EventArgs e)
        {

            if (txtPrice.Text == "" || txtPrice.Text == "0")
            {
                 txtPrice.Text = "";
                //txtCash.SelectionStart = 0;
                //txtCash.SelectionLength = txtCash.Text.Length;
                
            }
            else
            {
                CalculatePrice();
            }
        }