How to: Filter Data in a View
This example shows how to filter data in a view.
Example
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");
}
Public Function Contains(ByVal de As Object) As Boolean
Dim order1 As Order = TryCast(de, Order)
Return (order1.Filled Is "No")
End Function
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 How to: 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;
}
else
{
e.Accepted = false;
}
}
}
For the complete example, see Data Binding Demo.