CODEWITHSUNDEEP
c#wpfxamlmvvm
Hank
Hank

Reputation: 2616

How to add Filtering to Josh Smith's MVVM msdn design

I have mimicked Josh Smith's design from http://msdn.microsoft.com/en-us/magazine/dd419663.aspx and would like to add filtering.

In the AllCustomersViewModel he creates an ObservableCollection of CustomerViewModel, which is linked to the xaml via the property AllCustomers

public ObservableCollection<CustomerViewModel> AllCustomers { get; private set; }

In the xaml AllCustomers is set as a CollectionViewSource.

In saying this, I would like advise on how to extend this functionality to include filtering. I am not to worried about the xaml side of things, more implementing it in the ViewModel.

Upvotes: 2

Views: 276

Answers (1)

Rohit Vats
Rohit Vats

Reputation: 81253

Actually you don't need CollectionViewSource at all to be defined in XAML. It can be done all in your ViewModel.

Directly bind collection to ListBox in your XAML:

<ListBox ItemsSource="{Binding AllCustomers}"/>

and in ViewModel you can apply filter by getting default CollectionView related to your collection like this:

ICollectionView defaultCollectionView = CollectionViewSource
                                       .GetDefaultView(AllCustomers);
defaultCollectionView.Filter = p => ((CustomerViewModel)p).IsCompany;

Assuming IsCompany is a bool property. Filter takes predicate (you can replace it with any delegate returning bool).

On a side note you can also apply sorting and grouping from ViewModel itself.

If you want to have CollectionViewSource in XAML, you can apply filter in code-behind.

<CollectionViewSource x:Key="MyCVS"
                      Source="{Binding AllCustomers}"
                      Filter="MyCVS_Filter"/>

and in code behind:

void MyCVS_Filter(object sender, FilterEventArgs e)
{
    CustomerViewModel item = e.Item as CustomerViewModel;
    if (item.IsCompany)
    {
        e.Accepted = true;
    }
    else
    {
        e.Accepted = false;
    }
}

Upvotes: 2

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