Question

Okay here’s the situation. Net 4 WPF NO Silverlight.

I have several Views that present a datagrid showing the contents of some observable collections e.g.

ObservableCollection<ClassAViewModel> sourceA;
ObservableCollection<ClassBViewModel> sourceB;
ObservableCollection<ClassCViewModel> sourceC;

The collections are populated by a call to the data access layer. I can display this data easily enough with a Usercontrol that contains a datagrid bound to the appropriate collection.
I have

• ClassAView and ClassAViewModel to
  control display of single ClassA
  data,
• ClassBView and ClassBViewModel to
  control display of single ClassB data
• ClassCView and ClassCViewModel to
  control display of single ClassC data

I also have:

• AllClassAView and AllClassAViewModel
  to display a DataGrid with data
  relating to all ClassA instances.

• AllClassBView and AllClassBViewModel
  to display a DataGrid with data
  relating to all ClassB instances.

  etc.

Now say that ClassA contains a subset of the ClassB collection and a subset of the ClassC collection etc.

In my resource file I have bound the ViewModels and their Views together in the following manner (vm and vw are the namespaces of where they are) :

<DataTemplate DataType="x:Type vm:ClassAViewModel}">
  <vw:ClassAView/>
</DataTemplate>

Now what I was hoping to do was use an AllClassBView or AllClassBViewModel within the ClassAView to display the subset of ClassB instances that relate to it.

What is the best way to call up this data?

Can I re-use the AllClassBView UserControl to display a subset of the ClassB ObservableCollection and what is the best way of doing this?

I don’t want to place any code within the ClassAView.cs file only within the ClassAView.xaml or ClassAViewModel.

Should I just add a new property to the AllClassBView and use that to filter the list? For example within ClassBViewModel where I generate the list of ClassBViewModels (for use in the DataGrid) I can use:

if(this.ClassA_Id!=0)
{
  List<ClassBViewModel> all = (from ClassB in this.DataRepository.GetClassBs().Where(x=>x.ClassA_Id == this.ClassA_Id) select new ClassBViewModel()).ToList();
}
else
{
  List<ClassBViewModel> all = (from ClassB in this.DataRepository.GetClassBs() select new ClassBViewModel()).ToList();
}

this.sourceB= new ObservableCollection<ClassBViewModel>(all);

Answer 1

Well I’ve cracked it.

My problem may not have come across as very clear.

Whether my solution is good practice or not I don’t know.

What I have done is as follows:

I placed an extra property into the AllClassBViewModel that allows me to filter its list of ClassBViewModels to those that relate to ClassA.

public ulong ClassA_Id{get;set;}

So now when the AllClassBViewModel builds its list of ClassBViewModels it can now filter them by:

if(this.ClassA_Id!=0)
{
  List<ClassBViewModel> all = (from ClassB in this.DataRepository.GetClassBs().Where(x=>x.ClassA_Id == this.ClassA_Id) select new ClassBViewModel()).ToList();
}
else
{
  List<ClassBViewModel> all = (from ClassB in this.DataRepository.GetClassBs() select new ClassBViewModel()).ToList();
}

this.sourceB= new ObservableCollection<ClassBViewModel>(all);

I added a property and field to my ClassAViewModel that were of the AllClassBViewModel type.

private AllClassBViewModel fieldAllClassBViewModel;
public AllClassBViewModel AllClassBVM{get{return this.fieldAllClassBViewModel;}}

I then added an entry to an AllClassBView into the ClassAView that had a data context bound to the AllClassBVM property within ClassAViewModel.

<vw:AllClassBView DataContext="{Binding AllClassBVM}"/>

No all I have to do is check through the command binding.