WPF ObservableCollection列表的屬性變更通知方法

效果展示

cs代碼

using Microsoft.Toolkit.Mvvm.ComponentModel;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Collections.Specialized;
using System.ComponentModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace MVVMToolkit框架學習.ViewModels
{
    /// <summary>
    /// 條目數據
    /// </summary>
    public class MaterialItem : ObservableObject
    {
        private double _price;

        public string Name { get; set; }

        public double Price
        {
            get => _price;
            set => SetProperty(ref _price, value);
        }

        public string Description { get; set; }
    }

    public class ObservableCollectionVM : ObservableObject
    {
        private double _price;

        private ObservableCollection<MaterialItem> _materialItems;

        public ObservableCollection<MaterialItem> MaterialItems
        {
            get => _materialItems;
            set => SetProperty(ref _materialItems, value);
        }

        public double Price
        {
            get => _price;
            set => SetProperty(ref _price, value);
        }

        public ObservableCollectionVM()
        {
            MaterialItems = new ObservableCollection<MaterialItem>();
            MaterialItems.CollectionChanged += (s, e) =>
            {
                //監聽元素變更事件,或者可以直接ForEach遍歷所有的Item
                switch (e.Action)
                {
                    case NotifyCollectionChangedAction.Add:
                        foreach (var item in e.NewItems)
                        {
                            //掛載屬性變更方法
                            (item as INotifyPropertyChanged).PropertyChanged += (s, e) =>
                            {
                                Price = MaterialItems.Sum(x => x.Price);
                            };
                        }
                        break;

                    case NotifyCollectionChangedAction.Remove:
                    case NotifyCollectionChangedAction.Replace:
                    case NotifyCollectionChangedAction.Move:
                    case NotifyCollectionChangedAction.Reset:
                    default:
                        break;
                }
            };

            MaterialItems.Add(new MaterialItem() { Name = "玻璃" });
            MaterialItems.Add(new MaterialItem() { Name = "大理石" });
            MaterialItems.Add(new MaterialItem() { Name = "地板" });
        }
    }
}

xaml代碼

<Window
    x:Class="MVVMToolkit框架學習.Views.ObservableCollectionView"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="clr-namespace:MVVMToolkit框架學習.Views"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:vm="clr-namespace:MVVMToolkit框架學習.ViewModels"
    Title="ObservableCollectionView"
    Width="800"
    Height="450"
    d:DataContext="{d:DesignInstance Type={x:Type vm:ObservableCollectionVM}}"
    mc:Ignorable="d">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="2*" />
            <RowDefinition Height="8*" />
        </Grid.RowDefinitions>
        <StackPanel
            HorizontalAlignment="Center"
            VerticalAlignment="Center"
            Orientation="Horizontal">
            <TextBlock
                FontSize="25"
                Text="總價" />
            <TextBlock
                Margin="15,0,0,0"
                FontSize="25"
                Text="{Binding Price, UpdateSourceTrigger=PropertyChanged}" />
        </StackPanel>

        <DataGrid
            Grid.Row="1"
            HorizontalAlignment="Center"
            ItemsSource="{Binding MaterialItems}" />
    </Grid>
</Window>