WPF数据绑定

数据绑定是一个很强大且优雅的技能，之前用过好多次，但有些地方总不是特别清晰，常常需要重新翻阅资料来回顾，于是这次用了几天时间好好梳理一下，记录一下。

首先数据绑定对数据对象的要求：需要是公有属性（不支持字段和私有属性）。

如果需要在数据内容发生变化时自动更新到控件，则需要实现INotifyPropertyChanged接口，其包含 PropertyChanged事件，在属性变化时引发PropertyChanged事件。

如果绑定对象为集合时，需要在集合内容发生变化时自动更新到控件，则需要INotifyCollectionChanged接口，其包含CollectionChanged事件，目前内置的泛型集合 ObservableCollection 实现了该接口。

通常在设置绑定时，我们需要指定数据上下文，DataContext，如果控件没有设置DataContext，则会去找父容器的DataContext，依层级依次查找。也有些控件直接在代码中指定ItemsSource的。如果要绑定的数据依赖于另外一个控件的值，可以在DataContext中，绑定到另外一个控件的选中项，然后设置该控件的数据源或者绑定值。

MainWindow.xaml

<Window x:Class="TestBinding.MainWindow"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:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"xmlns:local="clr-namespace:TestBinding"mc:Ignorable="d"Title="MainWindow" Height="450" Width="800"><StackPanel Name="parentContainer"><StackPanel Orientation="Horizontal"><TextBlock>BindData:</TextBlock><TextBox Text="{Binding Path=BindData}"></TextBox></StackPanel><StackPanel Orientation="Horizontal"><TextBlock>BindDatas:</TextBlock><ListBox Name="exchangeListBox" ItemsSource="{Binding Path=Exchanges}" DisplayMemberPath="ExchangeID"></ListBox></StackPanel><StackPanel><ComboBox Name="instrumentCombbox" DataContext="{Binding ElementName=exchangeListBox, Path=SelectedItem}" ItemsSource="{Binding Path=Instruments}" DisplayMemberPath="InstrumentID"/></StackPanel><StackPanel Orientation="Horizontal" DataContext="{Binding ElementName=instrumentCombbox, Path=SelectedItem}"><TextBlock>ExchangeID:</TextBlock><TextBox Text="{Binding Path=ExchangeID}"></TextBox></StackPanel><StackPanel Orientation="Horizontal" DataContext="{Binding ElementName=instrumentCombbox, Path=SelectedItem}"><TextBlock>InstrumentID:</TextBlock><TextBox Text="{Binding Path=InstrumentID}"></TextBox></StackPanel><StackPanel Orientation="Horizontal" DataContext="{Binding ElementName=instrumentCombbox, Path=SelectedItem}"><TextBlock>InstrumentName:</TextBlock><TextBox Text="{Binding Path=InstrumentName}"></TextBox></StackPanel></StackPanel>
</Window>

MainWindow.xaml.cs

using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Runtime.CompilerServices;
using System.Windows;namespace TestBinding;public class ViewModelBase : INotifyPropertyChanged
{public event PropertyChangedEventHandler? PropertyChanged;protected virtual void OnPropertyChanged([CallerMemberName] string? propertyName = null){PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(propertyName));}protected virtual bool SetProperty<T>(ref T member, T value, [CallerMemberName] string? propertyName = null){if (EqualityComparer<T>.Default.Equals(member, value)){return false;}member = value;OnPropertyChanged(propertyName);return true;}
}
public class ExchangeViewModel : ViewModelBase
{private string exchangeID = string.Empty;public string ExchangeID { get => exchangeID; set => SetProperty(ref exchangeID, value); }public ObservableCollection<InstrumentViewModel> Instruments { get; set; } = new ObservableCollection<InstrumentViewModel>();
}
public class InstrumentViewModel : ViewModelBase
{public InstrumentViewModel(string exchangeID, string instrumentID, string instrumentName){ExchangeID = exchangeID;InstrumentID = instrumentID;InstrumentName = instrumentName;}private string _exchangeID = string.Empty;private string _instrumentID = string.Empty;private string _instrumentName = string.Empty;public string ExchangeID { get => _exchangeID; set => SetProperty(ref _exchangeID, value); }public string InstrumentID { get => _instrumentID; set => SetProperty(ref _instrumentID, value); }public string InstrumentName { get => _instrumentName; set => SetProperty(ref _instrumentName, value); }
}
/// <summary>
/// Interaction logic for MainWindow.xaml
/// </summary>
public partial class MainWindow : Window
{public MainWindow(){InitializeComponent();parentContainer.DataContext = this;Exchanges = new();ExchangeViewModel exchange1 = new ExchangeViewModel();exchange1.ExchangeID = "SHSE";exchange1.Instruments.Add(new InstrumentViewModel("SHSE", "601155", "新城控股"));exchange1.Instruments.Add(new InstrumentViewModel("SHSE", "600036", "招商银行"));exchange1.Instruments.Add(new InstrumentViewModel("SHSE", "600266", "城建发展"));exchange1.Instruments.Add(new InstrumentViewModel("SHSE", "600837", "海通证券"));exchange1.Instruments.Add(new InstrumentViewModel("SHSE", "601668", "中国建筑"));ExchangeViewModel exchange2 = new ExchangeViewModel();exchange2.ExchangeID = "SZSE";exchange2.Instruments.Add(new InstrumentViewModel("SZSE", "000002", "万科A"));exchange2.Instruments.Add(new InstrumentViewModel("SZSE", "000001", "平安银行"));exchange2.Instruments.Add(new InstrumentViewModel("SZSE", "000623", "吉林敖东"));exchange2.Instruments.Add(new InstrumentViewModel("SZSE", "002739", "万达电影"));exchange2.Instruments.Add(new InstrumentViewModel("SZSE", "300642", "透景生命"));Exchanges.Add(exchange1);Exchanges.Add(exchange2);}public string BindData { get; set; } = "BindData";public ObservableCollection<ExchangeViewModel> Exchanges { get; set; }
}