问题
I have a problem. I am trying to create a context menu with databinding in wpf. The context menu items would are bound to an observable collection of objects. The population of context menu is fine - however, I want to add the command to it.
The way I am using it is:
in XAML
<Grid.Resources>
<local:RestoreCommand x:Key="RestoreCommand" />
<local:ShowBalloonCommand x:Key="BaloonCommand" />
<local:StartTaskCommand x:Key="StartTaskCommand" />
</Grid.Resources>
<ContextMenu ItemsSource="{Binding}" Name="taskBarContextMenu">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Command" Value="{StaticResource StartTaskCommand}"/>
<Setter Property="CommandParameter" Value="{Binding mainWindow}"/>
</Style>
</ContextMenu.ItemContainerStyle>
and
<TextBlock TextWrapping="Wrap" Text="{Binding Name}" Grid.Column="0"/>
<TextBlock TextWrapping="Wrap" Text="{Binding TimeElapsed, Mode=TwoWay,UpdateSourceTrigger=PropertyChanged}" Grid.Column="2"/>
and in C#:
taskbarIcon.ContextMenu.ItemsSource = TasksList;
And I have a class for the command
public class StartTaskCommand : ICommand
{
public void Execute(object parameter)
{
//THE PARAMETER IS ALWAYS NULL
var window = parameter as MainWindow;
if (window != null)
{
}
}
public bool CanExecute(object parameter)
{
return true;
}
public event EventHandler CanExecuteChanged;
}
I have it set up simiarly for other two commands and it works fine. Anything I try to add as the parameter is always null - be it taskBarContextMenu, or mainWindow or menuItem... Any ideas welcome.
====
I tried a following solution as suggested, but the command parameter is still null:
<tb:TaskbarIcon Name="taskbarIcon"
DoubleClickCommand="{StaticResource RestoreCommand}"
DoubleClickCommandParameter="{Binding ElementName=mainWindow}"
LeftClickCommand="{StaticResource BaloonCommand}"
LeftClickCommandParameter="{Binding ElementName=mainWindow}"
IconSource=".\256px-Out_of_date_clock_icon.ico"
MenuActivation="RightClick"
Tag="{Binding ElementName=mainWindow}"
>
<tb:TaskbarIcon.ContextMenu ><ContextMenu DataContext="{Binding Path=PlacementTarget.Tag, RelativeSource={RelativeSource Self}}" Tag="{Binding}" Name="taskBarContextMenu">
<ContextMenu.ItemContainerStyle>
<Style TargetType="MenuItem">
<Setter Property="Command" Value="{StaticResource StartTaskCommand}"/>
<Setter Property="CommandParameter" Value="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}, Path=PlacementTarget.DataContext}"/>
</Style>
</ContextMenu.ItemContainerStyle>
回答1:
You need to add a tag to the menu's container and bind to it using placement target.
View this example:
<StackPanel x:Key="ConfigurationListItem" x:Shared="False" Tag="{Binding ElementName=UserControl}">
<StackPanel Orientation="Horizontal">
<Button>
<Button.InputBindings>
<MouseBinding Gesture="LeftDoubleClick" Command="{Binding ElementName=UserControl, Path=LaunchCommand}" CommandParameter="{Binding}" />
<MouseBinding Gesture="LeftClick" Command="{Binding ElementName=UserControl, Path=SelectCommand}" CommandParameter="{Binding}" />
</Button.InputBindings>
</StackPanel>
<StackPanel.ContextMenu>
<ContextMenu DataContext="{Binding Path=PlacementTarget.Tag, RelativeSource={RelativeSource Self}}" Tag="{Binding}">
<MenuItem Header="Sync Environment Dependencies"
Command="{Binding Parent.PlacementTarget.Tag.SyncEnvironmentCommand, RelativeSource={RelativeSource Self}}"
CommandParameter="{Binding RelativeSource={RelativeSource FindAncestor, AncestorType={x:Type ContextMenu}}, Path=PlacementTarget.DataContext}" />
</ContextMenu>
</StackPanel.ContextMenu>
</StackPanel>
来源:https://stackoverflow.com/questions/29010998/wpf-contextmenu-itemtemplate-commandparameter-binding-returns-null