C#：如何找到函数内数组的总和？

Question

我必须创建一个函数，使我能够为五金店中的每个客户输入数据。我应该为每个客户输入的数据是：名字、姓氏、购买的产品及其价格。此数据应存储在数组中。让这个函数声明一个 1D 容器，让用户用上述数据初始化这个 1D 容器，让这个函数把这个 1D 容器返回给 MAIN。在 MAIN 中，调用此函数 3 次，为 3 个客户创建数据。

之后，我需要创建另一个函数，将来自 MAIN 的所有三个 1D 客户数据容器作为参数，并将他们购买的产品的所有价格相加。让这个函数将总成本返回给 MAIN。 （这就是我卡住的地方。）

最后，我需要创建一个过程，将返回给 MAIN 的总成本作为参数，并确定这个总价格（设置为简单整数）是否是质数：

如果价值是质数，打印：“客户赢得价格” 否则，打印：“客户不会得到价格”

我被第二个函数卡住了，我试图做一个 C 风格的 for 循环，但它不起作用。

我尝试将这三个价格添加为带有索引但没有的数组位置。

这是我的代码：

using System;

namespace ghghh
{
    class Program
    {
        public static string [] inputData()
        {
            Console.WriteLine("Please enter your first name: ");
            string FirstName = Console.ReadLine();

            Console.WriteLine("Please enter your last name: ");
            string LastName = Console.ReadLine();

            Console.WriteLine("Please enter the product you ahve bought: ");
            string product = Console.ReadLine();

            Console.WriteLine("Please enter the price: ");
            string price = Console.ReadLine();

            string[] info = new string[4] { FirstName, LastName, product, price };

            return info; 

        }

        public static void sumOfPrice(string[] arr)
        {
            

            for(int i = 0; i<arr.Length; i++)
            {
                string sum = arr[i] + arr[i] + arr[i];
            }


            
        }

        public static void isTotalCostPrime(int n)
        {
            if(n %2 == 0)
            {
                Console.WriteLine("Customers wont get get the prize.");
            }
            else
            {
                Console.WriteLine("Customers win the prize");
            }
        }


        public static void Main (string[] args)
        {
            string[] final = inputData();
            sumOfPrice(final);
            

        }
    }
}

Answer 1

在这里，您可以部分解决您的问题。我将价格设为十进制数字（因为大多数货币都是十进制的）。这会排除你的 prime test 最后。

我还包括了一个数量。我很想为每个项目取出名字和姓氏（因为它需要大量输入）。不过，总而言之，这应该足以让您开始使用。

我从一个 POCO 类开始来保存购买的物品（POCO 代表“Plain Old CLR Object”；它是一个纯粹由 properties 组成的类。它是一个有点像老式的 C struct。

public class PurchasedItem
{
    public string FirstName { get; set; }
    public string LastName { get; set; }
    public string ProductName { get; set; }
    public int Quantity { get; set; }
    public decimal Price { get; set; }
}

我将用户界面分离到一个单独的类中（出于关注点分离的原因）。您可以轻松地将其折叠成一个类：

public class ItemUserInterface
{
    public static PurchasedItem PromptForItem()
    {
        var purchasedItem = new PurchasedItem();
        Console.Write("What is your First Name (or type \"exit\" if complete)? > ");
        var firstName = Console.ReadLine();
        if (firstName.Equals("exit", StringComparison.OrdinalIgnoreCase))
        {
            return null;
        }
        purchasedItem.FirstName = firstName;
        Console.Write("What is your Last Name? > ");
        purchasedItem.LastName = Console.ReadLine();
        Console.Write("What did you purchase? > ");
        purchasedItem.ProductName = Console.ReadLine();
        purchasedItem.Quantity = PromptForInteger("How many did you buy");
        purchasedItem.Price = PromptForDecimal("What was the price");
        Console.WriteLine(""); //empty line
        return purchasedItem;
    }

    public static void ShowPurchase (PurchasedItem item)
    {
        Console.WriteLine($"{item.FirstName} {item.LastName} bought {item.Quantity} of {item.ProductName} at {item.Price} each");
    }

    public static int PromptForInteger(string prompt)
    {
        while (true)
        {
            Console.Write(prompt + " > ");
            var entered = Console.ReadLine();
            if (int.TryParse(entered, out var result))
            {
                return result;
            }
            //otherwise error
            Console.WriteLine("Sorry, you must enter a proper integer value");
        }
    }

    public static decimal PromptForDecimal(string prompt)
    {
        while (true)
        {
            Console.Write(prompt + " > ");
            var entered = Console.ReadLine();
            if (decimal.TryParse(entered, out var result))
            {
                return result;
            }
            //otherwise error
            Console.WriteLine("Sorry, you must enter a proper decimal value");
        }
    }
}

顺便说一句，while (true) 将永远循环，除非您在循环之外执行 return 或 break 之类的操作。请注意，我一遍又一遍地提示用户，直到他/她输入格式正确的数字（对于数字条目）。

最后，这是我的Main 例程：

var itemsList = new List<PurchasedItem>();
while (true)
{
    var item = ItemUserInterface.PromptForItem();
    if (item == null)
    {
        break;
    }
    itemsList.Add(item);
}

// at this point, everything is entered
var totalPurchasePrice = 0.00m;
var totalItemsCount = 0;

foreach (var item in itemsList)
{
    ItemUserInterface.ShowPurchase(item);
    totalPurchasePrice += (item.Quantity * item.Price);
    totalItemsCount += item.Quantity;
}

Console.WriteLine($"Purchase Summary: {itemsList.Count} different items ({totalItemsCount} total items) for {totalPurchasePrice:C}");
Console.ReadLine(); //pause

}

如果我运行这个程序，输出看起来像：

What is your First Name (or type "exit" if complete)? > Fly
What is your Last Name? > Dog57
What did you purchase? > Cabbage
How many did you buy > 2
What was the price > 1.99

What is your First Name (or type "exit" if complete)? > Fly
What is your Last Name? > Dog57
What did you purchase? > Hammer
How many did you buy > 6
What was the price > abc
Sorry, you must enter a proper decimal value
What was the price > 10.55

What is your First Name (or type "exit" if complete)? > exit
Fly Dog57 bought 2 of Cabbage at 1.99 each
Fly Dog57 bought 6 of Hammer at 10.55 each
Purchase Summary: 2 different items (8 total items) for $67.28