Available for: Windows 8.1 | Windows Phone 8.1

Delegate Filter Descriptor

The DelegateFilterDescriptor exposes the following property:

  • Filter: Gets or sets the IFilter implementation used to check whether a data item passes the filter or not.

To use a DelegateFilterDescriptor you need to create a class that implements the IFilter interface which will return the Key you want to filter by.

Then you need to add a DelegateFilterDescriptor to the RadDataGrid.FilterDescriptors collection and set its Filter property.


Here's a simple example demonstrating how use a custom DelegateFilterDescriptor - we will create a grid containing countires and cities and we will filter the items by the length of the country name.

Create a custom class that implements the IFilter interface where the context we receive is our object:

public class CustomFilter : IFilter
    public bool PassesFilter(object item)
        if ((item as CustomData).Country.Length < 6)
            return true;
            return false;

As you can see, in this case the key we filter by is the number of letters of each Country. If a Country matches the condition to contain less than 6 letters - it passes the filter.

Then we set it to the Filter property of the DelegateFilterDescriptor:

<grid:RadDataGrid x:Name="grid" Width="300" VerticalAlignment="Center">

Create sample data and set it as ItemsSource of our the DataGrid:

List<CustomData> data = new List<CustomData>
    new CustomData { Country = "Brazil", City = "Caxias do Sul" },
    new CustomData { Country = "Brazil", City = "Fortaleza" },
    new CustomData { Country = "Spain", City = "Malaga" },
    new CustomData { Country = "Bulgaria", City = "Koynare" },
    new CustomData { Country = "Spain", City = "Valencia" },
    new CustomData { Country = "Ghana", City = "Kade" },
    new CustomData { Country = "Brazil", City = "Porto Alegre" },
    new CustomData { Country = "Bulgaria", City = "Byala Slatina" },
    new CustomData { Country = "Brazil", City = "Joinville" },
this.grid.ItemsSource = data;

CustomData is a custom class defining our objects:

public class CustomData
    public string Country { get; set; }

    public string City { get; set; }

And this is the result - the first picture shows the RadDataGrid before passing the filter, and the second - after filtering:

Delegate Filter Descriptor Example