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 Function Contains(ByVal de As Object) As Boolean
Dim order1 As Order = TryCast(de, Order)
Return (order1.Filled Is "No")
End Function
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.
Me.myCollectionView.Filter = New Predicate(Of Object)(AddressOf Me.Contains)
myCollectionView.Filter = new Predicate<object>(Contains);
To undo filtering, you can set the Filter property to null:
Me.myCollectionView.Filter = Nothing
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.
AddHandler listingDataView.Filter, AddressOf ShowOnlyBargainsFilter
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 Sub ShowOnlyBargainsFilter(ByVal sender As Object, ByVal e As FilterEventArgs)
Dim product As AuctionItem = CType(e.Item, AuctionItem)
If Not (product Is Nothing) Then
'Filter out products with price 25 or above
If product.CurrentPrice < 25 Then
e.Accepted = True
Else
e.Accepted = False
End If
End If
End Sub
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;
}
}
}