How to: Filter Data in a View


This example shows how to filter data in a view.

To create a filter, define a method that provides the filtering logic. The method is used as a callback and accepts a parameter of type object. The following method returns all the Order objects with the filled property set to "No", filtering out the rest of the objects.

    public bool Contains(object de)
        Order order = de as Order;
        //Return members whose Orders have not been filled
        return(order.Filled== "No");

You can then apply the filter, as shown in the following example. In this example, myCollectionView is a ListCollectionView object.

          myCollectionView.Filter = new Predicate<object>(Contains);

To undo filtering, you can set the Filter property to null:

          myCollectionView.Filter = null;

For information about how to create or obtain a view, see Get the Default View of a Data Collection. For the complete example, see Sorting and Filtering Items in a View Sample.

If your view object comes from a CollectionViewSource object, you apply filtering logic by setting an event handler for the Filter event. In the following example, listingDataView is an instance of CollectionViewSource.

            listingDataView.Filter += new FilterEventHandler(ShowOnlyBargainsFilter);

The following shows the implementation of the example ShowOnlyBargainsFilter filter event handler. This event handler uses the Accepted property to filter out AuctionItem objects that have a CurrentPrice of $25 or greater.

        private void ShowOnlyBargainsFilter(object sender, FilterEventArgs e)
            AuctionItem product = e.Item as AuctionItem;
            if (product != null)
                // Filter out products with price 25 or above
                if (product.CurrentPrice < 25)
                    e.Accepted = true;
                    e.Accepted = false;

Data Binding Overview
Sort Data in a View
How-to Topics