WPF ItemsControl Button命令绑定不起作用

Question

我有一个ItemsControl控件,它有一个ObservableCollection作为其ItemsSource.它还有一个位于DataTemplate内部的按钮.按钮的Command属性绑定到ViewModel中的RelayCommand(我使用的是MVVM Light),CommandParameter绑定到ItemsSource中的相应项.
问题是由于某种原因,命令永远不会触发.另一方面,代码隐藏工作正常.调试鼠标单击事件处理程序时,我可以看到发送方(类型为Button)的CommandParameter填充了正确的数据,而Command为null.

我在这里想念的是什么？

XAML:

<ItemsControl ItemsSource="{Binding Users}"
              Margin="{StaticResource ContentMargin}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel Orientation="Horizontal" />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Button Margin="{StaticResource ImageButtonMargin}"
                    Style="{StaticResource ImageButtonStyle}"
                    Command="{Binding RelativeSource={RelativeSource AncestorType={x:Type ItemsControl}}, Path=DataContext.UserSelectedCommand}"
                    CommandParameter="{Binding}">
                    <!--...-->

视图模型:

private ObservableCollection<User> _users;
private RelayCommand<User> _userSelectedCommand;

public ObservableCollection<User> Users
{
    get { return _users; }
    set
    {
        _users = value;
        RaisePropertyChanged();
    }
}

public RelayCommand<User> UserSelectedCommand
{
    get { return _userSelectedCommand; }
}

protected override sealed void SetCommands() // called in the constructor which is in turned called by SimpleIoc
{
     userSelectedCommand = new RelayCommand<User>((user) => UserSeriesSelected(user));
}

private void UserSelected(User selectedUser)
{

}

Answer 1

使用命名元素绑定作为数据模板内的绑定源,以从根数据上下文访问命令.您可以使用根网格或其他容器作为命名元素.ItemsControl iteself也可以使用.

<ItemsControl x:Name="MyItems" ItemsSource="{Binding Users}"
              Margin="{StaticResource ContentMargin}">
    <ItemsControl.ItemsPanel>
        <ItemsPanelTemplate>
            <WrapPanel Orientation="Horizontal" />
        </ItemsPanelTemplate>
    </ItemsControl.ItemsPanel>
    <ItemsControl.ItemTemplate>
        <DataTemplate>
            <Button Margin="{StaticResource ImageButtonMargin}"
                    Style="{StaticResource ImageButtonStyle}"
                    Command="{Binding ElementName=MyItems,  Path=DataContext.UserSelectedCommand}"
                    CommandParameter="{Binding}">
                    <!--...-->

Answer 2

您需要将“FindAncestor”添加到相对源绑定中：RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ItemsControl}}