是否有可能不在每個輸入的列表框中添加新行？

Question

我有一個winforms應用程序，它接受用戶輸入，並將其添加到列表中。此列表然後顯示在列表框中。

我的問題是，我希望列表框只在一行上顯示一次單個項目。 目前，它應該是這樣的：

Product Price Quantity 
Bread  1.20  1 
Bread  2.40  2 
Bread  3.60  3 
Eggs  1.50  1 
Eggs  3.00  2 

我會把它想顯示：

Product Price Quantity 
Bread  3.60  3 
Eggs  3.00  2 

是否有可能實現這一目標？

private void btnAdd_Click(object sender, EventArgs e) 
    { 
     lbBasket.DisplayMember = "ProductName"; 
     try 
     { 
      string name = textBoxProduct.Text.ToString(); 
      decimal price = Convert.ToDecimal(textBoxPrice.Text); 
      int quantity = Convert.ToInt32(textBoxQuantity.Text); 

      if (string.IsNullOrWhiteSpace(textBoxQuantity.Text)) 
      { 
       shoppingBasket.AddProduct(name, price); 
       lbBasket.Items.Add(textBoxProduct.Text); 
       lbPrice.Items.Add(shoppingBasket.BasketTotal); 
       lbQuantity.Items.Add(shoppingBasket.NumberOfTotalQuantities); 
      } 
      else 
      { 
       shoppingBasket.AddProduct(name, price, quantity); 
       lbPrice.Items.Add(shoppingBasket.BasketTotal); 
       lbQuantity.Items.Add(shoppingBasket.NumberOfTotalQuantities); 

       foreach (OrderItem item in shoppingBasket) 
       { 
        if (item.ProductName == name) 
        { 
         lbBasket.Items.Add(item.ProductName); 
        } 
       } 
      } 
     } 

Answer 1

這裏是你展示瞭如何使用一個列表框一個完整的例子。

using System; 
using System.Linq; 
using System.Windows.Forms; 

namespace WindowsFormsApplication1 
{ 
    public partial class Form1 : Form 
    { 
     public Form1() 
     { 
      InitializeComponent(); 
      lbBasket.Items.Add(new Basket("Name 1", (decimal) 1.00, 1)); 
      lbBasket.Items.Add(new Basket("Name 2", (decimal) 2.00, 2)); 
     } 

     private void btnAdd_Click(object sender, EventArgs e) 
     { 
      var newItem = new Basket(txtName.Text, Convert.ToDecimal(txtPrice.Text), Convert.ToInt32(txtQuantity.Text)); 

      var existingItem = 
       lbBasket.Items.Cast<Basket>() 
        .FirstOrDefault(li => li.Name.Equals(newItem.Name, StringComparison.OrdinalIgnoreCase)); 
      // There is something there 
      if (existingItem != null) 
      { 
       // You already have the best one 
       if (existingItem.Price > newItem.Price) 
       { 
        // Do nothing 
        return; 
       } 
       // Price is the same 
       if (existingItem.Price == newItem.Price) 
       { 
        lbBasket.Items.Remove(existingItem); 
        newItem.Quantity += existingItem.Quantity; 
        lbBasket.Items.Add(newItem); 
       } 
       // Remove the old item and add the new one 
       else if (existingItem.Price < newItem.Price) 
       { 
        lbBasket.Items.Remove(existingItem); 
        lbBasket.Items.Add(newItem); 
       } 
      } 
      else 
      { 
       lbBasket.Items.Add(newItem); 
      } 
     } 
    } 

    public class Basket 
    { 
     public string Name { get; set; } 
     public decimal Price { get; set; } 
     public int Quantity { get; set; } 

     public Basket(string name, decimal price, int quantity) 
     { 
      Name = name; 
      Price = price; 
      Quantity = quantity; 
     } 

     public override string ToString() 
     { 
      return Name + " £" + Price + " " + Quantity; 
     } 
    } 
} 

當你不指定DisplayMember然後調用toString被調用，所以我已經覆蓋比籃類來顯示你可能會喜歡它顯示。根據自己的需要編輯它，但是這有你需要的基本登錄信息，並且應該可以幫助你。如果您有任何問題隨時問... :)

邏輯是，如果名稱已經存在，那麼它會檢查價格，如果價格是相同的新項目，它會檢查數量，如果數量更高，它會更新。如果價格更高，它會更新。在所有其他情況下，不會進行更新。

Answer 2

只需添加類似的代碼如下：

foreach(listboxitem itm in lbBasket) 
{ 
    if(itm.toString()!=textBoxProduct.Text) 
    { 
    lbBasket.Items.Add(textBoxProduct.Text); 
    } 
} 

同樣保持環爲您在所有3個列表框。

Answer 3

你可以用LINQ做到這一點：

class Program 
{ 
    static void Main(string[] args) 
    { 
     List<ShoppingBasket> bag = new List<ShoppingBasket>(); 

     bag.Add(new ShoppingBasket("Bread", 1.20M, 1)); 
     bag.Add(new ShoppingBasket("Bread", 2.40M, 2)); 
     bag.Add(new ShoppingBasket("Bread", 3.60M, 3)); 

     bag.Add(new ShoppingBasket("Eggs", 1.50M, 1)); 
     bag.Add(new ShoppingBasket("Eggs", 3.000M, 2)); 


     var result = from x in bag 
        group x by x.Product into g 
        select new ShoppingBasket(g.Key, g.Max(x => x.Price), 
        g.Max(x => x.Quantity)); 
    } 
} 
public class ShoppingBasket 
{ 
    public string Product { get; set; } 
    public decimal Price { get; set; } 
    public int Quantity { get; set; } 

    public ShoppingBasket(string product, decimal price, int quantity) 
    { 
     this.Product = product; 
     this.Price = price; 
     this.Quantity = quantity; 
    } 
}