c# - CommandParameter 始终为空 wpf MVVM

Question

我想得到 NamePlaylist的Item我点击一个MenuContext。但是参数总是空的，我不知道为什么。

这是 ListView 中的菜单

XML

<MenuItem Header="Add" ItemsSource="{Binding Path=ItemSourcePlaylist}">
   <i:Interaction.Triggers>
      <i:EventTrigger EventName="Click">
         <i:InvokeCommandAction Command="{Binding TestCall}" CommandParameter="{Binding NamePlaylist}"/>
      </i:EventTrigger>
   </i:Interaction.Triggers>
   <MenuItem.ItemTemplate>
      <DataTemplate>
         <TextBlock Name="NamePlaylistText" Text="{Binding Path=NamePlaylist}"/>
      </DataTemplate>
   </MenuItem.ItemTemplate>
</MenuItem>

命令提供者

public class CommandProvider : ICommand
    {
    #region Constructors       

    public CommandProvider(Action<object> execute) : this(execute, null) { }

    public CommandProvider(Action<object> execute, Predicate<object> canExecute)
    {
        _execute = execute;
        _canExecute = canExecute;
    }

    #endregion

    #region ICommand Members

    public event EventHandler CanExecuteChanged;

    public bool CanExecute(object parameter)
    {
        return _canExecute != null ? _canExecute(parameter) : true;
    }

    public void Execute(object parameter)
    {
        if (_execute != null)
            _execute(parameter);
    }

    public void OnCanExecuteChanged()
    {
        CanExecuteChanged(this, EventArgs.Empty);
    }

    #endregion

    private readonly Action<object> _execute = null;
    private readonly Predicate<object> _canExecute = null;
    }

调用

public ICommand TestCall { get { return new RelayCommand(obj => this._settingsFunction.TestFunction(obj)); } }

功能

public void TestFunction(object o)
        {
            var tmp = o as string;
            Console.WriteLine(tmp);
            Console.WriteLine("TestMdr");
        }

Answer 1

如果我了解您的 View 模型，那么 ItemSourcePlaylist和 TestCall属于一类和NamePlaylist是 ItemSourcePlaylist 的属性(property)元素。如果是这种情况，我建议使用 ItemsContainerStyle并绑定(bind)Command parent 的属性(property)DataContext和 CommandParameter到当前项目的 DataContext

<MenuItem Header="Add" ItemsSource="{Binding Path=ItemSourcePlaylist}">
   <MenuItem.ItemContainerStyle>
       <Style TargetType="{x:Type MenuItem}">
           <Setter Property="Command" Value="{Binding RelativeSource={RelativeSource AncestorType={x:Type MenuItem}}, Path=DataContext.TestCall}"/>
           <Setter Property="CommandParameter" Value="{Binding NamePlaylist}"/>
       </Style>
   </MenuItem.ItemContainerStyle>
   <MenuItem.ItemTemplate>
       <DataTemplate>
           <TextBlock Name="NamePlaylistText"  Text="{Binding Path=NamePlaylist}"/>
       </DataTemplate>
   </MenuItem.ItemTemplate>
</MenuItem>