使用关键字“价值”在Set Concector C＃中

Question

我正在尝试在设置访问者中使用关键字value，只要用户输入的值大于0，我就想将其设置为变量ventity。

我似乎找不到我做错了什么。对于此Quantity = value;，我一直在收到回溯错误。希望有人能看到我没有的东西。谢谢。

using System;

namespace Invoice
{
    class MainClass
    {
        public static void Main(string[] args)
        {
            Console.WriteLine("How many parts would you like to " +
                "enter into the system: ");
            int newParts = int.Parse(Console.ReadLine());

            Invoice[] invoice = new Invoice[newParts];

            for (int i = 0; i < newParts; i++)
            {
                invoice[i] = new Invoice();

                Console.WriteLine("Enter the part number: ");
                invoice[i].PartNumber = Console.ReadLine();

                Console.WriteLine("Enter description of item: ");
                invoice[i].PartDescription = Console.ReadLine();

                Console.WriteLine("Enter the quantity: ");
                invoice[i].Quantity = int.Parse(Console.ReadLine());

                Console.WriteLine("Enter in the price of the item: ");
                invoice[i].PricePerItem = decimal.Parse(Console.ReadLine());
            }

            for (int i = 0; i < newParts; i++)
            {
                invoice[i].DisplayOrder();

            }
        }
    }
}


using System;
namespace Invoice
{
    public class Invoice
    {
        public string PartNumber { get; set; }
        public string PartDescription { get; set; }

        public int Quantity
        {
            get { return Quantity; }

            set
            {
                if (value >= 0)
                {
                    Quantity = value;
                }

                if (value <= 0)
                {
                    Quantity = Quantity;
                }
            }
        }

        public decimal PricePerItem
        {
            get
            {
                return PricePerItem;
            }

            set
            {
                if(value >= 0.0m)
                {
                    PricePerItem = value;
                }

                if (value <= 0.0m)
                {
                    PricePerItem = PricePerItem;
                }
            }
        }

        public Invoice(String PartNumber, String PartDescription, int Quantity, decimal PricePerItem)
        {
            this.PartNumber = PartNumber;
            this.PartDescription = PartDescription;
            this.Quantity = Quantity;
            this.PricePerItem = PricePerItem;
        }

        public Invoice()
        {
        }

        public decimal GetInvoiceAmount(int numberOfItems, decimal priceOfItem)
        {
            return numberOfItems * priceOfItem;
        }

        public void DisplayOrder()
        {
            decimal total = GetInvoiceAmount(Quantity, PricePerItem);

            // Display Receipt
            Console.Write("\nOrder Receipt: ");

            Console.WriteLine($"\nPart Number: {PartNumber}");

            Console.WriteLine($"Unit Price: {PricePerItem:C}");

            Console.WriteLine($"Quantity: {Quantity}");

            Console.WriteLine($"Part Description: {PartDescription}");

            Console.WriteLine($"Total price: {total:C}");
        }

 
    }
}

Answer 1

这没有道理：

if (value >= 0)
{
    Quantity = value;
}

if (value <= 0)
{
    Quantity = Quantity;
}

为什么要为自己设置财产？那无法实现任何有用的东西。您说，只有当分配的值大于零时，您想设置属性，那么为什么除了大于零以外的任何内容，为什么要检查value？

if (value > 0)
{
    Quantity = value;
}

就是这样。

也就是说，如果该值无效，而不是仅仅默默地不设置属性，则您也应该扔grognal ungeofrangeException。这样做的逻辑方式就是这样：

if (value <= 0)
{
    throw new ArgumentOutOfRangeException(...);
}

Quantity = value;

现在，只有在不引发异常时才会设置属性值。

我也只是意识到您没有此属性的支持字段，所以这是错误的。整个事情应该看起来像这样：

private int quantity;

public int Quantity
{
    get { return quantity; }

    set
    {
        if (value <= 0)
        {
            throw new ArgumentOutOfRangeException(...);
        }

        quantity = value;
    }
}

Answer 2

错误是因为在您的集合{}中，您正在递归调用同一设置器。

        private int quantity; 
        public int Quantity
        {
            get { return  this.quantity; }

            set
            {
                if (value >= 0)
                {
                     this.quantity= value;
                }
            }
        }

        private decimal pricePerItem;
        public decimal PricePerItem
        {
            get
            {
                return  this.pricePerItem;
            }

            set
            {
                if(value >= 0.0m)
                {
                     this.pricePerItem= value;
                }
            }
        }