wpf 为什么这个按钮命令绑定不起作用？
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Why this Button Command Binding is not working?
提问by Xelom
I did this like 50 times before. I really don't know why it is not working this time. I have a WPF application and my only dependency is MahApps.Metro. I'm using it's MetroWindow and Dynamic Style on my Button.
我以前这样做过 50 次。我真的不知道为什么这次不起作用。我有一个 WPF 应用程序，我唯一的依赖项是 MahApps.Metro。我在我的按钮上使用它的 MetroWindow 和 Dynamic Style。
Here is the latest xaml:
这是最新的xaml：
<ItemsControl Grid.Column="0" Grid.Row="1" ItemsSource="{Binding ServerList}" Margin="5">
<ItemsControl.ItemTemplate>
<DataTemplate>
<Border Background="LightGray">
<StackPanel Orientation="Horizontal">
<Button Style="{DynamicResource MetroCircleButtonStyle}" Content="{StaticResource appbar_monitor}" Command="{Binding VM.ServerSelectedCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=Controls:MetroWindow}}" CommandParameter="{Binding .}"></Button>
<Label Content="{Binding .}" HorizontalAlignment="Center" VerticalAlignment="Center"></Label>
</StackPanel>
</Border>
</DataTemplate>
</ItemsControl.ItemTemplate>
</ItemsControl>
Here is my ServerSelectedCommand in my ViewModel:
这是我的 ViewModel 中的 ServerSelectedCommand：
private ViewModelCommand _ServerSelectedCommand;
public ViewModelCommand ServerSelectedCommand
{
get
{
if (_ServerSelectedCommand == null)
{
_ServerSelectedCommand = new ViewModelCommand(
p => { SelectServer(p); },
p => true
);
}
return _ServerSelectedCommand;
}
set { _ServerSelectedCommand = value; }
}
private void SelectServer(object parameter)
{
}
ViewModelCommand class is like RelayCommand. Here it is:
ViewModelCommand 类就像 RelayCommand。这里是：
public class ViewModelCommand : Observable, ICommand
{
public bool CanExecuteValue
{
get { return CanExecute(null); }
}
public ViewModelCommand(
Action<object> executeAction,
Predicate<object> canExecute)
{
if (executeAction == null)
throw new ArgumentNullException("executeAction");
_executeAction = executeAction;
_canExecute = canExecute;
}
private readonly Predicate<object> _canExecute;
public bool CanExecute(object parameter)
{
return _canExecute == null ? true : _canExecute(parameter);
}
public event EventHandler CanExecuteChanged;
public void OnCanExecuteChanged()
{
OnPropertyChanged(() => CanExecuteValue);
if (CanExecuteChanged != null)
CanExecuteChanged(this, EventArgs.Empty);
}
private readonly Action<object> _executeAction;
public void Execute(object parameter)
{
_executeAction(parameter);
}
}
Sorry for a lot of code. But I need to add them in order to find the problem which I can't see. So lets turn back to first xaml, that is the latest one I tried. Here are the codes that I tried for problematic Button line.
抱歉有很多代码。但是我需要添加它们才能找到我看不到的问题。所以让我们回到第一个 xaml，这是我尝试过的最新一个。这是我为有问题的 Button 行尝试的代码。
Command="{Binding ServerSelectedCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ItemsControl}}"
Command="{Binding ServerSelectedCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType={x:Type local:ViewModel}}}"
This also doesn't provide anything!
这也没有提供任何东西！
Command="{Binding RelativeSource={RelativeSource AncestorType=Controls:MetroWindow}}"
Thanks!
谢谢！
回答by Peter Holmes
This binding looks like it is looking for ServerSelectedCommand on the ItemsControl:
这个绑定看起来像是在 ItemsControl 上寻找 ServerSelectedCommand：
Command="{Binding ServerSelectedCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ItemsControl}}"
try this instead:
试试这个：
Command="{Binding DataContext.ServerSelectedCommand, RelativeSource={RelativeSource Mode=FindAncestor, AncestorType=ItemsControl}}"
Assuming of course that the DataContext of the ItemsControl is your ViewModel.
当然，假设 ItemsControl 的 DataContext 是您的 ViewModel。
