如何从后面的代码访问DataTemplate内部的视图

Question

I'm binding my viewmodel and view using resource dictionary as follows

<DataTemplate DataType="{x:Type viewmodels:MyViewModel}">
    <Views:MyView />
</DataTemplate>

in MyView, i have dataGrid x:Name="BoxDataGrid" with DataGrid.RowDetailsTemplate having other dataGrid x:Name="SpoolsDataGrid"

how to access MyView or datagrids above using code behind in MyViewModel ?

The reason is,i want to load and show contents inside RowDetailsTemplate only when main datagrid row selected (clicked) thru event "RowDetailsVisibilityChanged".

Thanks.

Correction: My bad. I want to access MyView not MyViewModel

Answer 1

It's quite easy. DataContext property in your MyView object points to concrete object of MyViewModel . So you can use XAML bindings to this view-model or access in code-behind eg

MyViewModel model = (MyViewModel) DataContext;

Answer 2

asktomsk's answer is correct. You can access the ViewModel via the DataContext property.

However, with a little bit more effort you can almost always get around directly accessing the ViewModel from the view. The whole point of MVVM or MVC is that there aren't dependencies from View to ViewModel.

Things you should research in WPF for MVVM include:

• Attached Properties
• Attached Behaviors
• Mediators
• Value Converters
• Markup Extensions

You need to be aware of all of these to find elegant solutions to some problems you encounter with MVVM.

You'll need to specify a bit more detail about the behaviour you are trying to get if you want us to help you figure out how you can do it without accessing the ViewModel through the datacontext.

You can, for instance, bind somethings' Visibility to a boolean in the ViewModel using a converter?

I apologize if you know all of the above already.

Answer 3

Just solved this problem using MVVM Light Toolkit - EventToCommand. Other better suggestions are very much welcome.

http://blog.galasoft.ch/archive/2009/11/05/mvvm-light-toolkit-v3-alpha-2-eventtocommand-behavior.aspx

Hope this solution will be useful to others. don't need to know the view, in my datagrid view

  <i:Interaction.Triggers>
      <i:EventTrigger EventName="RowDetailsVisibilityChanged">
         <cmd:EventToCommand Command="{Binding RowDetailsVisibilityChangedCommand}" PassEventArgsToCommand="True" />
      </i:EventTrigger>
  </i:Interaction.Triggers>

and in viewmodel

    public RelayCommand<DataGridRowDetailsEventArgs> RowDetailsVisibilityChangedCommand
    {
        get;
        private set;
    }

and in viewmodel constructor

 RowDetailsVisibilityChangedCommand = new RelayCommand<DataGridRowDetailsEventArgs>(e =>
{
   DataGrid SpoolsDataGrid = e.DetailsElement as DataGrid;
   DataRowView drv = (DataRowView)e.Row.Item;
   serialNo = drv.Row["BOX_SERIAL"].ToString();
   SpoolsDataGrid.ItemsSource = as400Service.GetSPOOL_BY_SERIAL_NO(serialNo);
 });