输出文本框中的文本而不是多行，在文本框属性中将换行设置为true

我需要winform的文本框是多行的，但我不知道怎么做。它只是一行。自动换行设置为true。我是否也必须在代码中设置为true？我是不是搞砸了格式？我不确定我做错了什么。这是代码：

public override string  ToString()
    {
        return string.Format("{0} Pizzas @ {1:C}: {2:C}'n" +
            "{3} Cokes @ {4:C}  {5:C}'n" +
            "Order Amount: {6:C}'n" +
            "Sales Tax: {7:C}'n" +
            "Amount Due: {8:C}'n" +
            "Amount Paid: {9:C}'n" +
            "Change Due: {10:C}", numberOfPizzas, PIZZA_PRICE, 
            totalCostOfPizza, numberOfCokes, COKE_PRICE, totalCostOfCoke,
            foodAndDrinkTotal, totalSalesTax, totalAmountDue, amountPaid, 
            changeDue);
    }        
........
private void btnPaymentButton_Click(object sender, EventArgs e)
    {            
        amountPaid = double.Parse(this.txtAmountPaid.Text);
        orderPaymentObject = new Payment(orderObject.TotalAmountDue, amountPaid);
        this.txtNumberOfPizzaOrdered.Clear();
        this.txtNumberOfCokesOrdered.Clear();
        this.txtAmountDue.Clear();
        this.txtAmountPaid.Clear();
        this.lblYourOrder.Visible = true;
        this.txtYourOrder.Visible = true;
        this.txtYourOrder.Text =  orderObject.ToString();               
    }