为什么我不能绑定到按钮的命令？ [英] Why I can't bind the Command to the button?

问题描述

我在Windows Phone 7.5及以上版本的项目目标上工作。

我有

ListBox

 < ListBox Horizo​​ntalAlignment =Left
 VerticalAlignment =Top
 SelectedItem ={Binding singleFavListItem ，Mode = TwoWay}
 ItemTemplate ={StaticResource userFavBoardListItemTemplate}
 ItemsSource ={Binding userfavboardlist}
 ScrollViewer.VerticalScrollBarVisibility =DisabledMargin =12,0,0， 12/> 
  

ItemTemplate

 < DataTemplate x：Key =userFavBoardListItemTemplate> 
< Grid> 
< Grid.ColumnDefinitions> 
< ColumnDefinition Width =70 */> 
< ColumnDefinition Width =30 */> 
< /Grid.ColumnDefinitions> 
< TextBlock Horizo​​ntalAlignment =Left
 TextWrapping =Wrap
 Text ={Binding boardName}
 VerticalAlignment =Center
 FontSize ={ StaticResource PhoneFontSizeMedium}
 Foreground ={StaticResource TitleColor}/> 
< Button Command ={Binding quitBoardCommand}
 CommandParameter ={Binding boardUrl}
 Content =Quit
 Horizo​​ntalAlignment =Left
 VerticalAlignment =Top
 Grid.Column =1
 FontSize ={StaticResource PhoneFontSizeSmall}
 BorderBrush ={StaticResource DateArticalCategoryColor}
 Foreground ={StaticResource DateArticalCategoryColor} > 
< / Button> 
< / Grid> 
< / DataTemplate> 
  

ViewModel

  public MyFavListViewModel（）
 {
 this._quitBoardCommand = new DelegateCommand（this.quitBoardAction）; 
} 
 private ICommand _quitBoardCommand; 
 public ICommand quitBoardCommand 
 {
 get 
 {
 return this._quitBoardCommand; 
} 
} 
 private void quitBoardAction（object p）
 {
 //我的业务逻辑
} 
  
 
 
 
错误
 
我在OutPut窗口中发现错误：
 
 
 < blockquote> 
 
'xicihutong.Model.UserFavBoardListRawData'（HashCode = 55845053）。 
 BindingExpression：Path ='quitBoardCommand'
 DataItem ='xicihutong.Model.UserFavBoardListRawData'
（HashCode = 55845053）;目标元素是
'System.Windows.Controls.Button'（Name =''）;目标属性是
'Command'（输入'System.Windows.Input.ICommand'）.. 
 
 
 有什么问题 
 
什么让我困惑的是，当我点击按钮时，quitBoardCommand永远不会被触发？看来我不能将命令绑定到按钮，DelegateCommand部分是正确的，因为我可以使用它来绑定命令在其他页面。 
 
 
 
为什么我不能绑定这个呢？
解决方案
您需要引用 ListBox 的 DataContext 绑定到您的命令。要解决这个问题，请给你的 ListBox 一个名称，然后引用命令属性
 < ListBox x：Name =myLB
<！ - 其余的东西 - > 
 /> 
 
< Button 
 Command ={Binding Path = DataContext.quitBoardCommand，ElementName = myLB}
 CommandParameter ={Binding boardUrl}
 Content =退出/> 
  
 
I work on a project target on Windows Phone 7.5 and above.

What I have

ListBox
<ListBox    HorizontalAlignment="Left" 
        VerticalAlignment="Top" 
        SelectedItem="{Binding singleFavListItem, Mode=TwoWay}"
        ItemTemplate="{StaticResource userFavBoardListItemTemplate}"
        ItemsSource="{Binding userfavboardlist}" 
        ScrollViewer.VerticalScrollBarVisibility="Disabled" Margin="12,0,0,12"/>
ItemTemplate
<DataTemplate x:Key="userFavBoardListItemTemplate">
    <Grid>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="70*"/>
            <ColumnDefinition Width="30*"/>
        </Grid.ColumnDefinitions>
        <TextBlock  HorizontalAlignment="Left" 
            TextWrapping="Wrap" 
            Text="{Binding boardName}" 
            VerticalAlignment="Center" 
            FontSize="{StaticResource PhoneFontSizeMedium}" 
            Foreground="{StaticResource TitleColor}"/>
        <Button Command="{Binding quitBoardCommand}"
                CommandParameter="{Binding boardUrl}"
                Content="Quit" 
        HorizontalAlignment="Left" 
        VerticalAlignment="Top" 
        Grid.Column="1"
        FontSize="{StaticResource PhoneFontSizeSmall}" 
        BorderBrush="{StaticResource DateArticalCategoryColor}" 
        Foreground="{StaticResource DateArticalCategoryColor}">
     </Button>
    </Grid>
</DataTemplate>
ViewModel
public MyFavListViewModel()
{
    this._quitBoardCommand = new DelegateCommand(this.quitBoardAction);
}
private ICommand _quitBoardCommand;
public ICommand quitBoardCommand
{
    get
    {
        return this._quitBoardCommand;
    }
}
private void quitBoardAction(object p)
{
    //my business logic here
}
Error

I found a error in the OutPut windows:

  
'xicihutong.Model.UserFavBoardListRawData' (HashCode=55845053).
  BindingExpression: Path='quitBoardCommand'
  DataItem='xicihutong.Model.UserFavBoardListRawData'
  (HashCode=55845053); target element is
  'System.Windows.Controls.Button' (Name=''); target property is
  'Command' (type 'System.Windows.Input.ICommand')..
What's the problem

What confuse me is that the quitBoardCommand never get triggered when I tap the button? It seems that I can't bind the Command to the button, the DelegateCommand part is right, because I can use it to bind command in other pages. And the SelectedItem of the ListBox works right, also.

Why I can't bind this one?
解决方案
You need to reference the DataContext of your ListBox to bind to your command. To fix this, give your ListBox a name then reference the command property
<ListBox x:Name="myLB"
    <!-- rest of your stuff -->
/>

<Button 
    Command="{Binding Path=DataContext.quitBoardCommand, ElementName=myLB}"
    CommandParameter="{Binding boardUrl}"
    Content="Quit" />


                        
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