WPF Using multiple filters on the same ListCollectionView

Question

I\'m using the MVVM design pattern, with a ListView bound to a ListCollectionView on the ViewModel. I also have several comboboxes that are used to filter the ListView. When t

Answer 1

Every time the user filters, your code is replacing the Filter delegate in your collection view with a new, fresh one. Moreover, the new one only checks the particular criteria the user just selected with a ComboBox.

What you want is a single filter handler that checks all criteria. Something like:

public MyViewModel()
{
    products = new ObservableCollection();
    productsView = new ListCollectionView(products);
    productsView.Filter += FilterProduct;
}

public Item SelectedItem
{
    //get,set omitted. set needs to invalidate filter with refresh call
}

public Type SelectedType
{
    //get,set omitted. set needs to invalidate filter with refresh call
}

public Category SelectedCategory
{
    //get,set omitted. set needs to invalidate filter with refresh call
}

public ICollection FilteredProducts
{
    get { return productsView; }
}

private bool FilterProduct(object o)
{
    var product = o as Product;

    if (product == null)
    {
        return false;
    }

    if (SelectedItem != null)
    {
        // filter according to selected item
    }

    if (SelectedType != null)
    {
        // filter according to selected type
    }

    if (SelectedCategory != null)
    {
        // filter according to selected category
    }

    return true;
}

Your view can now just bind to the appropriate properties and the filtering will just work.