如何在MVMVM WPF中绑定父项或其他ViewModel属性

Question

Hi I had defined Property in My BookViewVM

   private Visibility _isLoaderPageView = Visibility.Hidden;
    public Visibility IsLoaderPageView
    {
        get
        {
            return _isLoaderPageView;
        }
        set
        {
            _isLoaderPageView = value;
            RaisePropertyChanged("IsLoaderPageView");
        }
    }

I am calling this bookViewVM on Page.xaml page but on Page.xaml some other PageViewVM had already bind But I have to call the BookViewVM Property:

<views:LoadingAnimation  x:Name="ldrControl"  Margin="100,100,100,150"   Visibility="{Binding IsLoaderPageView}"   />

I am able to access this BookViewVM Property on My Pageview.xaml.cs code Like this: ETBApp.MainVM.BookVM.IsLoaderPageView

But I have to call this from Property binding on page. please tell me how to bind it.

Both ViewModel like BookViewVm and PageViewVm on same namesapce.

Answer 1

The problem is that you have multiple DataContexts and by default Binding works with the DataContext of current element if it is specified, and datacontext of parent if not(and so on).

so there is 2 simple solutions:

• specify DataContext of element directly(only if that element does not have one)
• use ElementName (if you have access in xaml to specific element and it must be named properly through Name or x:Name ), or RelativeSource (if you bind to some ancestor ) inside Binding with Path

Answer 2

Just set properly DataContext. For example in grid

<Grid.DataContext>
  <viewmodel:YourViewModel />
</Grid.DataContext>

And now you can bind it

<ItemsControl ItemsSource="{Binding Model.ButtonsRaw1}">

There we bind ItemsSource from our model.

Or you have an alternative way to do it from Resource. SOmething like this

<UserControl.Resources>
        <Style TargetType="local:YourType">
            <Setter Property="Text" Value="{Binding Path=DataContext.Model.Text, Mode=TwoWay,ElementName=YourGridName}"/>
        </Style>
</UserControl.Resources>