WPF DataContext与Binding的关系

在前台UI创建一个Label绑定到myLabel

<Window x:Class="WpfApp1.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:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="300" Width="500">
    <Grid>
        <Label Content="{Binding myLabel}"/>
    </Grid>
</Window>

在后台代码赋值myLabel

using System.Windows;

namespace WpfApp1
{
    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow : Window
    {
        private string label = "我的标签";
        public string myLabel
        {
            get { return label; }
            set { label = value; }
        }
        public MainWindow()
        {
            InitializeComponent();
            DataContext = this;
        }
    }
}

运行如下

 这里的DataContext = this到底是什么呢？调试运行发现DataContext 其实就是MainWindow类

 如果我们自己新建一个类，让DataContext 等于这个新建的类是否可以呢？

 内容如下

namespace WpfApp1
{
    public class ClassA
    {
        private string label = "新建类A的标签";
        public string myLabel
        {
            get { return label; }
            set { label = value; }
        }
    }
}

MainWindow.xaml.cs里的DataContext = this改成 DataContex = new ClassA();其他的不变

    public partial class MainWindow : Window
    {
        private string label = "我的标签";
        public string myLabel
        {
            get { return label; }
            set { label = value; }
        }
        public MainWindow()
        {
            InitializeComponent();
            //DataContext = this;
            DataContext = new ClassA();
        }
    }

运行结果

 源码下载地址https://github.com/lizhiqiang0204/DataContext-and-Bingding.git

有朋友会有疑问，一个UI文件的DataContext只能指定一个类吗？不，是可以指定多个类的。

我们新建一个类ClassB

 其他文件不用动，只需修改UI文件

<Window x:Class="WpfApp1.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:WpfApp1"
        mc:Ignorable="d"
        Title="MainWindow" Height="300" Width="500">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="*"/>
            <RowDefinition Height="*"/>
        </Grid.RowDefinitions>
        <Grid>
            <Grid.DataContext>
                <local:ClassA/>
            </Grid.DataContext>
            <Label Content="{Binding myLabel}"/>
        </Grid>
        <Grid Grid.Row="1">
            <Grid.DataContext>
                <local:ClassB/>
            </Grid.DataContext>
            <Label Content="{Binding myLabel}"/>
        </Grid>
    </Grid>
</Window>

 多类之间如何互相访问呢？参考https://www.cnblogs.com/lizhiqiang0204/p/12582510.html