wpf 带有 MVVM 和 CommandParameter 的 ListBox SelectionChanged 事件
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ListBox SelectionChanged event with MVVM and CommandParameter
提问by VansFannel
I'm developing a MVVM app with WPF, C# and .NET Framework 4.6.1.
我正在使用 WPF、C# 和 .NET Framework 4.6.1 开发 MVVM 应用程序。
I'm trying to implement ListBox SelectionChangedevent using MVVM. To do it I have done this:
我正在尝试ListBox SelectionChanged使用 MVVM实现事件。为此，我已经这样做了：
Install nuget package: PM> Install-Package System.Windows.Interactivity.WPF.
Add xmlns:interactivity="http://schemas.microsoft.com/expression/2010/interactivity"on xaml.
Add this code to my ListBoxin xaml:
安装 nuget 包：PM> Install-Package System.Windows.Interactivity.WPF.
添加xmlns:interactivity="http://schemas.microsoft.com/expression/2010/interactivity"xaml。
将此代码添加到我ListBox的 xaml 中：
<ListBox x:Name="listBoxTrzType" Grid.Column="1" Margin="10,0,25,0" VerticalAlignment="Center" Height="25" ItemsSource="{Binding TrzTypes}">
<ListBox.ItemTemplate>
<DataTemplate>
<StackPanel>
<TextBlock Text="{Binding Name}"/>
</StackPanel>
</DataTemplate>
</ListBox.ItemTemplate>
<interactivity:Interaction.Triggers>
<interactivity:EventTrigger EventName="SelectionChanged">
<interactivity:InvokeCommandAction Command="{Binding ListBoxTrzTypeSelectionChanged}"
CommandParameter="{Binding ElementName=listBoxTrzType, Path=SelectedItem}">
</interactivity:InvokeCommandAction>
</interactivity:EventTrigger>
</interactivity:Interaction.Triggers>
</ListBox>
On ViewModel I have:
在 ViewModel 我有：
public ICommand ListBoxTrzTypeSelectionChanged
{
get { return new DelegateCommand(TrzTypeSelectionChanged); }
}
private void TrzTypeSelectionChanged()
{
throw new NotImplementedException();
}
And DelegateCommandclass:
和DelegateCommand类：
public class DelegateCommand : ICommand
{
private readonly Action _action;
public DelegateCommand(Action action)
{
_action = action;
}
public void Execute(object parameter)
{
_action();
}
public bool CanExecute(object parameter)
{
return true;
}
#pragma warning disable 67
public event EventHandler CanExecuteChanged { add { } remove { } }
#pragma warning restore 67
}
But my problem is that I don't know how to pass CommandParameter="{Binding ElementName=listBoxTrzType, Path=SelectedItem}"to private void TrzTypeSelectionChanged().
但我的问题是我不知道如何传递CommandParameter="{Binding ElementName=listBoxTrzType, Path=SelectedItem}"给private void TrzTypeSelectionChanged().
I've been searching a lot on Internet and I haven't found any example (only examples with CanExecute).
我在互联网上搜索了很多，但没有找到任何示例（只有带有 的示例CanExecute）。
How do I have to modify my ViewModelclass to access SelectedItemparameter?
我必须如何修改我的ViewModel类才能访问SelectedItem参数？
回答by Dennis
Actually, to use interaction behaviors for such task is overkill.
You even don't need a command here. It's enough to add SelectedItemproperty into view model and listen for property changes:
实际上，将交互行为用于此类任务是矫枉过正的。
你甚至不需要这里的命令。将SelectedItem属性添加到视图模型中并侦听属性更改就足够了：
public class SomeVm : INotifyPropertyChanged
{
// INPC implementation is omitted
public IEnumerable<SomeType> Items { get; }
public SomeType SelectedItem
{
get { return selectedItem; }
set
{
if (selectedItem != value)
{
selectedItem = value;
OnPropertyChanged();
// do what you want, when property changes
}
}
}
}
XAML:
XAML：
<ListBox ItemsSource="{Binding Items}"
SelectedItem="{Binding SelectedItem}"
DisplayMemberPath="Name"/>
回答by XAMlMAX
In your DelegateCommand
change private readonly Action _action;to private readonly Action<object> _action;then in your execute method
在您DelegateCommand
更改private readonly Action _action;为private readonly Action<object> _action;then 在您的执行方法中
public void Execute(object parameter)
{
_action.Invoke(parameter);
}
Now your ViewModelfunction needs to look like this:
现在您的ViewModel函数需要如下所示：
private void TrzTypeSelectionChanged(object parameter)
{
throw new NotImplementedException();
}
And you are good to go.
你很高兴去。
