c# - 如何在 wpf 的用户控件中使用命令绑定(bind)？

Question

在 MainWindow 中，命令绑定(bind)工作正常。在 UserControl1 中它不起作用。请注意，数据上下文已正确设置，正如绑定(bind)结果按钮的内容所证明的那样。

我并没有尝试将用户控件中的命令绑定(bind)到主窗口中的命令或任何其他此类技巧。我只是想在 UserControl1 中复制我在 MainWindow 中所做的事情。

主窗口 XAML

<StackPanel>
    <Button Content="Click Here" Command="{Binding ClickHereCommand}" Height="25" Width="90"></Button>
    <local:UserControl1></local:UserControl1>
</StackPanel>

MainWindow 代码隐藏

public partial class MainWindow : Window
{
    public static RoutedCommand ClickHereCommand { get; set; }

    public MainWindow()
    {
        InitializeComponent();
        this.DataContext = this;
        ClickHereCommand = new RoutedCommand();
        CommandBindings.Add(new CommandBinding(ClickHereCommand, ClickHereExecuted));
    }

    public void ClickHereExecuted(object sender, ExecutedRoutedEventArgs e)
    {
        System.Windows.MessageBox.Show("hello");
    }
}

用户控件 XAML

<UserControl x:Class="CommandBindingTest.UserControl1"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
         xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006" 
         xmlns:d="http://schemas.microsoft.com/expression/blend/2008" 
         mc:Ignorable="d" 
         d:DesignHeight="300" d:DesignWidth="300" x:Name="root">

<Grid DataContext="{Binding ElementName=root}" >
    <Button Content="{Binding ButtonContent}" Command="{Binding ClickHereCommand}" Height="25" Width="90"></Button>
</Grid>
</UserControl>

用户控制代码隐藏

public partial class UserControl1 : UserControl, INotifyPropertyChanged
{
    private string _ButtonContent;
    public string ButtonContent
    {
        get { return _ButtonContent; }
        set
        {
            if (_ButtonContent != value)
            {
                _ButtonContent = value;
                OnPropertyChanged("ButtonContent");
            }
        }
    }

    public static RoutedCommand ClickHereCommand { get; set; }


    public UserControl1()
    {
        InitializeComponent();
        ClickHereCommand = new RoutedCommand();
        CommandBindings.Add(new CommandBinding(ClickHereCommand, ClickHereExecuted));
        ButtonContent = "Click Here";
    }

    public void ClickHereExecuted(object sender, ExecutedRoutedEventArgs e)
    {
        System.Windows.MessageBox.Show("hello from UserControl1");
    }


    #region INotifyPropertyChanged Members
    public event PropertyChangedEventHandler PropertyChanged;

    public void OnPropertyChanged(string name)
    {
        if (PropertyChanged != null)
        {
            PropertyChanged(this, new PropertyChangedEventArgs(name));
        }
    }
    #endregion
}

Answer 1

这是最好的解决方案:

 <Grid DataContext="{Binding RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type UserControl}}}" >
        <Button Content="{Binding ButtonContent}" Command="{Binding ClickHereCommand}" Height="25" Width="90"></Button>
 </Grid>

其他解决方案:

您忘记将 DataContext 设置为 UserControl1。

  public UserControl1()
        {
            InitializeComponent();
            ClickHereCommand = new RoutedCommand();
            CommandBindings.Add(new CommandBinding(ClickHereCommand, ClickHereExecuted));
            ButtonContent = "Click Here";
            this.DataContext = this;
        }

在此之后，您必须删除 Grid 中的 UserControl1 DataContext。

这个:

<Grid DataContext="{Binding ElementName=root}" >
    <Button Content="{Binding ButtonContent}" Command="{Binding ClickHereCommand}" Height="25" Width="90"></Button>
</Grid>

你必须改成这样:

<Grid>
        <Button Content="{Binding ButtonContent}" Command="{Binding ClickHereCommand}" Height="25" Width="90"></Button>
</Grid>

在UserControl中不设置DataContext的解决方法:

您必须将 ButtonContent 和 ClickHereCommand 更改为 DependencyProperty。

        public string ButtonContent
        {
            get { return (string)GetValue(ButtonContentProperty); }
            set { SetValue(ButtonContentProperty, value); }
        }

        public static readonly DependencyProperty ButtonContentProperty =
            DependencyProperty.Register("ButtonContent", typeof(string), typeof(UserControl1), new UIPropertyMetadata(string.Empty));

        public RoutedCommand ClickHereCommand
        {
            get { return (RoutedCommand)GetValue(ClickHereCommandProperty); }
            set { SetValue(ClickHereCommandProperty, value); }
        }

        public static readonly DependencyProperty ClickHereCommandProperty =
            DependencyProperty.Register("ClickHereCommand", typeof(RoutedCommand), typeof(UserControl1), new UIPropertyMetadata(null));

在 UserControl1 的构造函数中:

 public UserControl1()
    {
        InitializeComponent();

        ClickHereCommand = new RoutedCommand();
        CommandBindings.Add(new CommandBinding(ClickHereCommand, ClickHereExecuted));            
        ButtonContent = "Click Here";
        //this.DataContext = this;
    }