我如何获得列表框中项目价格的总和？

Question

按钮1-10是项目；the pos screenshot

我使用过但无法使用的代码，也许是错误的，但我无法在互联网上找到答案

private void enterPayment_Click(object sender, EventArgs e)
{
    label1.Text = "Payment";
    //price.ReadOnly = false;
    //price.Text = "0.00";
    //price.Focus();

    //Kukunin ko yung total ng List Items
    double total = 0;
    int ilan = orders.Items.Count;

    for (int i = 0; i >= ilan; i++)
    {
        string item = orders.Items[i].ToString();
        int Index = item.IndexOf("@");
        int Length = item.Length;
        string presyoString = item.Substring(Index + 1, Length - Index - 1);
        double presyoDouble = double.Parse(presyoString);
        total += presyoDouble;
        //price.Text = (total + ".00");
    }
    price.Text = (total + ".00");
}

Answer 1

我强烈建议您仅将列表框用作视图，而不要用于执行数学运算。可以在列表等集合中使用该数据，以便执行更好的操作。

例如，在程序加载时，我将在List<T>和表单上添加产品信息，我在按钮中放置了一个标签，将其视为产品ID。因此，当我单击按钮时，它将传递tag属性，然后从那里，我将在列表中搜索有关我的ID的产品信息，并将其添加到另一个最终的List<T>中并获取其总和。

public partial class Form1 : Form
{
    private List<ProductDisplay> listProductDisplay = new List<ProductDisplay>();
    private List<ProductInformation> listProductInfo = new List<ProductInformation>();
    public Form1()
    {
        InitializeComponent();
        LoadProduct();

    }
    private void LoadProduct()
    {
        listProductDisplay = new List<ProductDisplay>()
        {
            new ProductDisplay{ProdID = 1,ProdName = "Chargrilled Burger",ProdPrice = 330.00m},
            new ProductDisplay{ProdID = 2,ProdName = "Mushroom N' Swish",ProdPrice = 330.00m},
            new ProductDisplay{ProdID = 3,ProdName = "Chicken Burger",ProdPrice = 250.00m},
            new ProductDisplay{ProdID = 4,ProdName = "Steak Loader",ProdPrice = 220.00m},
            new ProductDisplay{ProdID = 5,ProdName = "Cookie Sandwich",ProdPrice = 125.00m},
            new ProductDisplay{ProdID = 6,ProdName = "Cookie Sundae",ProdPrice = 175.00m},
            new ProductDisplay{ProdID = 7,ProdName = "Chicken Nuggets",ProdPrice = 145.00m},
            new ProductDisplay{ProdID = 8,ProdName = "Curly Fries",ProdPrice = 75.00m},
            new ProductDisplay{ProdID = 9,ProdName = "Sprite",ProdPrice = 50.00m},
            new ProductDisplay{ProdID = 10,ProdName = "Coke",ProdPrice = 50.00m}
        };
    }

    private void InsertOrder_ButtonClick(object sender, EventArgs e)
    {
        try
        {
            Button btn = (Button)sender;
            int number = Convert.ToInt32(btn.Tag);
            var itemProduct = listProductDisplay.First(x => x.ProdID == number);
            ProductInformation prod = new ProductInformation
            {
                ProdID = itemProduct.ProdID,
                ProdName = itemProduct.ProdName,
                ProdPrice = itemProduct.ProdPrice,
                ProdQty = 1

            };
            prod.ProdDisplayName = $"{prod.ProdQty}x {prod.ProdName} @{prod.ProdPrice.ToString("F")} = {(prod.ProdPrice * prod.ProdQty).ToString("F")}";
            listProductInfo.Add(prod);
            listBoxItem.DataSource = null;
            listBoxItem.DataSource = listProductInfo;
            listBoxItem.DisplayMember = "ProdDisplayName";
            listBoxItem.ValueMember = "ProdID";

            var price = listProductInfo.Sum(t => (t.ProdPrice * t.ProdQty));
            txtPayment.Text = price.ToString("F");
        }
        catch (Exception ex)
        {
            MessageBox.Show("Failed to insert order");
            throw;
        }
    }
}
public class ProductDisplay
{
    public int ProdID { get; set; }
    public string ProdName { get; set; }
    public decimal ProdPrice { get; set; }
}
public class ProductInformation
{
    public int ProdID { get; set; }
    public string ProdName { get; set; }
    public string ProdDisplayName { get; set; }
    public decimal ProdPrice { get; set; }
    public int ProdQty { get; set; }
}

Answer 2

您可以使用Linq和Regex计算价格。例如

var regex = new Regex(@"=\W*(?<Price>([\d.]*))");
var total = orders.Select(x=> regex.Match(x.ToString()))
                      .Cast<Match>()
                      .Sum(x=>double.Parse(x.Groups["Price"].Value));

Regex "=\W*(?<Price>([\d.]*))"将允许您匹配=字符后的小数部分。然后，您可以使用它来计算total。

样本

输入

2 x Something @ 1 = 2.00 
3 x Something @ 2 = 6.00 
1 x Something @ 3 = 3.00 
3 x Something @ 4 = 12.00 
1 x Something @ 5 = 5.00 
2 x Something @ 6 = 12.00 
2 x Something @ 7 = 14.00 
3 x Something @ 8 = 24.00 
2 x Something @ 9 = 18.00 
2 x Something @ 10 = 20.00 

输出

116

Answer 3

从这样的字符串中解析和提取值非常容易出错并且很脆弱。如果您的行中的字段顺序发生变化，会发生什么？还是添加货币符号？

@ Luiey的解决方案是最明智的方法。但是，如果由于某种原因您不能对代码进行太多更改，那么您要做的最低限度就是将项目作为自定义对象存储在列表中，其中包含价格，数量和总计的静态类型字段。 ListBox类在呈现项目时调用ToString()。因此，您可以轻松地重写此方法以根据需要准备输出字符串。

private class LineItem
{
    public LineItem()
    {
        Quantity = 0;
        Description = string.Empty;
        Price = 0;
    }

    public int Quantity
    {
        get;
        set;
    }

    public string Description
    {
        get;
        set;
    }

    public int Price
    {
        get;
        set;
    }

    public int Total
    {
        get
        {
            return Quantity * Price;
        }
    }

    public override string ToString()
    {
        return $"{Quantity} × {Description} @ {Price} = {Total}";
    }
}

然后您像这样将一个项目添加到列表框。

var item = new LineItem()
{
    Quantity = 1,
    Description = "Foo bar",
    Price = 10
};
listBox1.Items.Add(item);

并像这样将它们加起来。

var items = listBox1.Items.Cast<LineItem>().ToArray();
var accumulator = 0;
accumulator = items.Aggregate(accumulator, (a, i) => a + (i.Quantity * i.Price), (a) => a);