我正在为一个酒吧创建一个EPOS系统，我的项目只是为了测试我的技能。
我遇到了问题，我已经设法将所有产品放在WrapPanel中，点击后我也设法让它们在ListView控件中显示。
但是，我似乎无法将总数显示在ListView下方的标签中，实际上，每次将产品添加到ListView时，我希望通过将所有价格中的所有价格相加来更新总数。价格“列并在下面的标签中显示。但我甚至无法通过按钮打印总数，更不用说自动执行了。
到目前为止，这是我的按钮代码。
不要建议SubItems，因为它在WPF中不起作用。
private void Button_Click_1(object sender, RoutedEventArgs e) {
decimal total = 0;
foreach (ListViewItem o in orderDetailsListView.Items)
{
total = total + (decimal)(orderDetailsListView.SelectedItems[1]);
}
totalOutputLabel.Content = total;
}
答案 0 :(得分：1)
我在下面回答了你的另一个问题，在你发布之前你删除了同一个程序。它涵盖了更新价格，但也涵盖了更多（使用已删除问题中的信息）。
首先，如果您希望在更新列表中的项目时更新屏幕，则必须使类实现INotifyPropertyChanged
public class OrderDetailsListItem : INotifyPropertyChanged
{
private string _name;
private decimal _price;
private int _quantity;
public string Name
{
get { return _name; }
set
{
if (value == _name) return;
_name = value;
OnPropertyChanged();
}
}
public decimal Price
{
get { return _price; }
set
{
if (value == _price) return;
_price = value;
OnPropertyChanged();
}
}
public int Quantity
{
get { return _quantity; }
set
{
if (value == _quantity) return;
_quantity = value;
OnPropertyChanged();
}
}
public event PropertyChangedEventHandler PropertyChanged;
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
现在，当价格或数量发生变化时，它会让绑定知道该项目已被更改。
接下来，您if (OrderItem.Contains(导致重复项目显示的原因是您必须实施Equals(（最好是GetHashCode()）才能使Contains(工作。
public class OrderDetailsListItem : INotifyPropertyChanged, IEquatable<OrderDetailsListItem>
{
//(Snip everything from the first example)
public bool Equals(OrderDetailsListItem other)
{
if (ReferenceEquals(null, other)) return false;
return string.Equals(_name, other._name);
}
public override bool Equals(object obj)
{
return Equals(obj as OrderDetailsListItem);
}
public override int GetHashCode()
{
return (_name != null ? _name.GetHashCode() : 0);
}
}
另一点，在点击按钮时不要OrderItem.CollectionChanged +=，您将在每次收集更改事件时创建额外的事件调用。只需在构造函数中设置一个，这是您需要的唯一偶数订阅。但是，有一个更好的集合可供使用BindingList<T>及其ListChanged事件。 BindingList将在ObserveableCollection引发CollectionChanged的所有情况下引发ListChange事件，但此外，当集合中的任何项引发INotifyPropertyChanged事件时，它也会引发事件。
public MainWindow()
{
_orderItem = new BindingList<OrderDetailsListItem>();
_orderItem.ListChanged += OrderItemListChanged;
InitializeComponent();
GetBeerInfo();
//You will see why all the the rest of the items were removed in the next part.
}
private void OrderItemListChanged(object sender, ListChangedEventArgs e)
{
TotalPrice = OrderItem.Select(x => x.Price).Sum();
}
最后，我打赌你来自Winforms背景。 WPF基于绑定比winforms更多，我以前编写的代码很像你在我真正接受这一点之前所做的事情。所有这些标签和集合的赋值应该在XAML中完成，带有绑定，这允许用于像INotifyPropertyChanged事件一样自动更新屏幕而无需函数调用。
这是一个简单的程序设计，它运行并使用绑定和我谈到的所有其他内容。
<Window x:Class="WpfApplication2.MainWindow"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
xmlns:myNamespace ="clr-namespace:WpfApplication2"
Title="MainWindow" Height="350" Width="525" >
<Grid>
<Grid.ColumnDefinitions>
<ColumnDefinition/>
<ColumnDefinition/>
</Grid.ColumnDefinitions>
<StackPanel Grid.Column="0">
<Button Content="{x:Static myNamespace:GlobalVariables._amstelProductName}" Click="amstelBeerButton_Click"/>
<TextBlock Text="{Binding TotalPrice, StringFormat=Total: {0:c}}"/>
</StackPanel>
<ListView Grid.Column="1" ItemsSource="{Binding OrderItem}">
<ListView.View>
<GridView>
<GridViewColumn DisplayMemberBinding="{Binding Path=Name}" Header="Name"/>
<GridViewColumn DisplayMemberBinding="{Binding Path=Price, StringFormat=c}" Header="Price"/>
<GridViewColumn DisplayMemberBinding="{Binding Path=Quantity, StringFormat=N0}" Header="Quantity"/>
</GridView>
</ListView.View>
</ListView>
</Grid>
</Window>
using System;
using System.ComponentModel;
using System.Linq;
using System.Runtime.CompilerServices;
using System.Windows;
namespace WpfApplication2
{
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{
public static readonly DependencyProperty TotalPriceProperty = DependencyProperty.Register(
"TotalPrice", typeof (decimal), typeof (MainWindow), new PropertyMetadata(default(decimal)));
private readonly BindingList<OrderDetailsListItem> _orderItem;
public MainWindow()
{
_orderItem = new BindingList<OrderDetailsListItem>();
_orderItem.ListChanged += OrderItemListChanged;
InitializeComponent();
DataContext = this;
GetBeerInfo();
}
public BindingList<OrderDetailsListItem> OrderItem
{
get { return _orderItem; }
}
public decimal TotalPrice
{
get { return (decimal) GetValue(TotalPriceProperty); }
set { SetValue(TotalPriceProperty, value); }
}
private void GetBeerInfo()
{
OrderItem.Add(new OrderDetailsListItem
{
Name = "Some other beer",
Price = 2m,
Quantity = 1
});
}
private void OrderItemListChanged(object sender, ListChangedEventArgs e)
{
TotalPrice = _orderItem.Select(x => x.Price).Sum();
}
private void amstelBeerButton_Click(object sender, RoutedEventArgs e)
{
//This variable makes me suspicous, this probibly should be a property in the class.
var quantityItem = GlobalVariables.quantityChosen;
if (quantityItem == 0)
{
quantityItem = 1;
}
var item = OrderItem.FirstOrDefault(i => i.Name == GlobalVariables._amstelProductName);
if (item == null)
{
OrderItem.Add(new OrderDetailsListItem
{
Name = GlobalVariables._amstelProductName,
Quantity = quantityItem,
Price = GlobalVariables._amstelPrice
});
}
else if (item != null)
{
item.Quantity = item.Quantity + quantityItem;
item.Price = item.Price*item.Quantity;
}
//The UpdatePrice function is nolonger needed now that it is a bound property.
}
}
public class GlobalVariables
{
public static int quantityChosen = 0;
public static string _amstelProductName = "Amstel Beer";
public static decimal _amstelPrice = 5;
}
public class OrderDetailsListItem : INotifyPropertyChanged, IEquatable<OrderDetailsListItem>
{
private string _name;
private decimal _price;
private int _quantity;
public string Name
{
get { return _name; }
set
{
if (value == _name) return;
_name = value;
OnPropertyChanged();
}
}
public decimal Price
{
get { return _price; }
set
{
if (value == _price) return;
_price = value;
OnPropertyChanged();
}
}
public int Quantity
{
get { return _quantity; }
set
{
if (value == _quantity) return;
_quantity = value;
OnPropertyChanged();
}
}
public bool Equals(OrderDetailsListItem other)
{
if (ReferenceEquals(null, other)) return false;
if (ReferenceEquals(this, other)) return true;
return string.Equals(_name, other._name);
}
public event PropertyChangedEventHandler PropertyChanged;
public override bool Equals(object obj)
{
return Equals(obj as OrderDetailsListItem);
}
public override int GetHashCode()
{
return (_name != null ? _name.GetHashCode() : 0);
}
protected virtual void OnPropertyChanged([CallerMemberName] string propertyName = null)
{
var handler = PropertyChanged;
if (handler != null) handler(this, new PropertyChangedEventArgs(propertyName));
}
}
}
答案 1 :(得分：0)
刚刚对此进行了测试，您应该确保通过添加断点进入事件处理程序。如果不是，请确保已将处理程序注册到click事件，例如：
<Button Name="TestButton" Click="Button_Click_1"/>
如果您正在使用WPF，我强烈建议您在某些时候查看MVVM和数据绑定。