# .NET MAUI CollectionView Filtering The CollectionView provides the functionality to programmatically filter its data at runtime. You can achieve this by adding different filter descriptors in the `RadCollectionView.FilterDescriptors` collection. The following descriptor types are supported: * [Text Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#text-filter-descriptor) * [Numerical Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#numerical-filter-descriptor) * [DateTime Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#datetime-filter-descriptor) * [TimeSpan Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#timespan-filter-descriptor) * [Boolean Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#boolean-filter-descriptor) * [Nested Property Text Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#nested-property-text-filter-descriptor) * [Distinct Values Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#distinct-values-filter-descriptor) * [Composite Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#composite-filter-descriptor) * [Delegate Filter Descriptor](https://www.telerik.com/maui-ui/documentation/controls/collectionview/filtering#delegate-filter-descriptor) All `FilterDescriptors` are located in the `Telerik.Maui.Controls.Data` namespace. ## Text Filter Descriptor The `TextFilterDescriptor` represents a descriptor which filters by properties of the `string` data type. The descriptor supports the following properties: * `PropertyName`—Defines the name of the property that is used to retrieve the filter value. * `Operator`—Defines the `TextOperator` value that defines how the `Value` member is compared with each value from the items source. * `Value`—Defines the value used in the comparisons. This is the right operand of the comparison. * `IsCaseSensitive`—Defines a value that determines whether the text comparisons will be case-sensitive. The default value is `true`. ### Example with Text Filter Descriptor The following example implements a `TextFilterDescriptor` and uses a [`RadEntry`](https://www.telerik.com/maui-ui/documentation/controls/entry/overview) control that allows the user to enter a string of text to filter the CollectionView data. **1.** Define the `RadCollectionView` and `RadEntry` in XAML: ```XAML ``` **2.** Add the `telerik` namespace: ```XAML xmlns:telerik="http://schemas.telerik.com/2022/xaml/maui" ``` **3.** Create a sample `DataModel`: ```C# public class DataModel : NotifyPropertyChangedBase { private string continent; private string country; private string city; private int id; public string Continent { get => this.continent; set => this.UpdateValue(ref this.continent, value); } public string Country { get => this.country; set => this.UpdateValue(ref this.country, value); } public string City { get => this.city; set => this.UpdateValue(ref this.city, value); } public int Id { get => this.id; set => this.UpdateValue(ref this.id, value); } } ``` **4.** Define the `ViewModel` class: ```C# public class ViewModel : NotifyPropertyChangedBase { public ViewModel() { this.Locations = new ObservableCollection { new DataModel { Continent = "Europe", Country = "Austria", City = "Graz", Id = 1 }, new DataModel { Continent = "Europe", Country = "Austria", City = "Innsbruck", Id = 2 }, new DataModel { Continent = "Europe", Country = "Austria", City = "Ratz", Id = 3 }, new DataModel { Continent = "Europe", Country = "Austria", City = "Vienna", Id = 4 }, new DataModel { Continent = "Europe", Country = "Belgium", City = "Antwerp", Id = 5 }, new DataModel { Continent = "Europe", Country = "Belgium", City = "Charleroi", Id = 6 }, new DataModel { Continent = "Europe", Country = "Belgium", City = "Schaffen", Id = 7 }, new DataModel { Continent = "Europe", Country = "Denmark", City = "Copenhagen", Id = 8 }, new DataModel { Continent = "Europe", Country = "Denmark", City = "Odense", Id = 9 }, new DataModel { Continent = "Europe", Country = "France", City = "Nice", Id = 10 }, new DataModel { Continent = "Europe", Country = "France", City = "Paris", Id = 11 }, new DataModel { Continent = "Europe", Country = "Germany", City = "Baden-Baden", Id = 12 }, new DataModel { Continent = "Europe", Country = "Germany", City = "Berlin", Id = 13 }, new DataModel { Continent = "Europe", Country = "Germany", City = "Hamburg", Id = 14 }, new DataModel { Continent = "Europe", Country = "Germany", City = "Munich", Id = 15 }, new DataModel { Continent = "Europe", Country = "Germany", City = "Nuremberg", Id = 16 }, new DataModel { Continent = "Europe", Country = "Italy", City = "Bari", Id = 17 }, new DataModel { Continent = "Europe", Country = "Italy", City = "Rome", Id = 18 }, new DataModel { Continent = "Europe", Country = "Netherlands", City = "Amsterdam", Id = 19 }, new DataModel { Continent = "Europe", Country = "Netherlands", City = "Eindhoven", Id = 20 }, new DataModel { Continent = "Europe", Country = "Netherlands", City = "Rotterdam", Id = 21 }, new DataModel { Continent = "Europe", Country = "Portugal", City = "Lisbon", Id = 22 }, new DataModel { Continent = "Europe", Country = "Portugal", City = "Porto", Id = 23 }, new DataModel { Continent = "Europe", Country = "Spain", City = "Barcelona", Id = 24 }, new DataModel { Continent = "Europe", Country = "Spain", City = "Madrid", Id = 25 }, new DataModel { Continent = "Europe", Country = "United Kingdom", City = "London", Id = 26 }, new DataModel { Continent = "Europe", Country = "United Kingdom", City = "Manchester", Id = 27 }, new DataModel { Continent = "North America", Country = "United States", City = "New York", Id = 28 }, new DataModel { Continent = "North America", Country = "United States", City = "Los Angeles", Id = 29 }, new DataModel { Continent = "North America", Country = "United States", City = "Chicago", Id = 30 }, new DataModel { Continent = "North America", Country = "United States", City = "Boston", Id = 31 }, new DataModel { Continent = "North America", Country = "United States", City = "San Francisco", Id = 32 }, new DataModel { Continent = "North America", Country = "Canada", City = "Toronto", Id = 33 }, new DataModel { Continent = "North America", Country = "Canada", City = "Vancouver", Id = 34 }, new DataModel { Continent = "North America", Country = "Canada", City = "Ottawa", Id = 35 }, new DataModel { Continent = "South America", Country = "Brazil", City = "Rio de Janeiro", Id = 36 }, new DataModel { Continent = "South America", Country = "Brazil", City = "Sao Paulo", Id = 37 }, new DataModel { Continent = "South America", Country = "Brazil", City = "Salvador", Id = 38 }, new DataModel { Continent = "South America", Country = "Argentina", City = "Buenos Aires", Id = 39 }, new DataModel { Continent = "South America", Country = "Peru", City = "Lima", Id = 40 }, new DataModel { Continent = "South America", Country = "Peru", City = "Cusco", Id = 41 }, new DataModel { Continent = "South America", Country = "Colombia", City = "Bogota", Id = 42 }, new DataModel { Continent = "South America", Country = "Bolivia", City = "La Paz", Id = 43 }, new DataModel { Continent = "South America", Country = "Venezuela", City = "Caracas", Id = 44 }, new DataModel { Continent = "South America", Country = "Chile", City = "Santiago", Id = 45 }, new DataModel { Continent = "Asia", Country = "China", City = "Hong Kong", Id = 46 }, new DataModel { Continent = "Asia", Country = "China", City = "Shanghai", Id = 47 }, new DataModel { Continent = "Asia", Country = "China", City = "Macau", Id = 48 }, new DataModel { Continent = "Asia", Country = "India", City = "Delhi", Id = 49 }, new DataModel { Continent = "Asia", Country = "India", City = "Hyderabad", Id = 50 }, new DataModel { Continent = "Asia", Country = "Japan", City = "Tokyo", Id = 51 }, new DataModel { Continent = "Asia", Country = "Japan", City = "Osaka", Id = 52 }, new DataModel { Continent = "Asia", Country = "Japan", City = "Kyoto", Id = 53 }, new DataModel { Continent = "Asia", Country = "Vietnam", City = "Ho Chi Minh", Id = 54 }, new DataModel { Continent = "Asia", Country = "Vietnam", City = "Hanoi", Id = 55 }, new DataModel { Continent = "Asia", Country = "Thailand", City = "Bangkok", Id = 56 }, new DataModel { Continent = "Asia", Country = "Thailand", City = "Phuket", Id = 57 }, new DataModel { Continent = "Africa", Country = "Nigeria", City = "Lagos", Id = 58 }, new DataModel { Continent = "Africa", Country = "Egypt", City = "Cairo", Id = 59 }, new DataModel { Continent = "Africa", Country = "Algeria", City = "Algiers", Id = 60 }, new DataModel { Continent = "Oceania", Country = "Australia", City = "Sydney", Id = 61 }, new DataModel { Continent = "Oceania", Country = "Australia", City = "Melbourne", Id = 62 }, new DataModel { Continent = "Oceania", Country = "Australia", City = "Canberra", Id = 63 }, new DataModel { Continent = "Oceania", Country = "New Zealand", City = "Auckland", Id = 64 }, new DataModel { Continent = "Oceania", Country = "New Zealand", City = "Wellington", Id = 65 }, }; } public ObservableCollection Locations { get; set; } } ``` **5.** Add the `TextFilterDescriptor` to the `RadCollectionView` inside the `RadEntry` `TextChanged` event: ```C# public partial class FilterDescriptor : ContentView { private TextFilterDescriptor descriptor; public FilterDescriptor() { InitializeComponent(); } private void OnFilterChanged(object sender, TextChangedEventArgs e) { var filterText = e.NewTextValue; if (this.descriptor != null) { this.collectionView.FilterDescriptors.Remove(this.descriptor); } this.descriptor = new TextFilterDescriptor { PropertyName = nameof(DataModel.City), IsCaseSensitive = false, Operator = TextOperator.Contains, Value = filterText, }; this.collectionView.FilterDescriptors.Add(this.descriptor); } } ``` This is the result: ![Telerik UI for .NET MAUI CollectionView filtered by text entered in the CollectionView data filter field](https://www.telerik.com/maui-ui/documentation/assets/189cf545666b148ef8232eb4428a89dc/collectionview-filtering.gif "Telerik .NET MAUI CollectionView") > For a runnable demo with the CollectionView Filtering example, see the [SDKBrowser Demo Application](https://www.telerik.com/maui-ui/documentation/demos-and-sample-apps/sdkbrowser-app) and go to the **CollectionView > Filtering** category. ## Numerical Filter Descriptor The `NumericalFilterDescriptor` represents a descriptor which filters by properties of the `numerical` data type. The descriptor exposes the following properties: * `PropertyName`—Defines the name of the property that is used to retrieve the filter value. * `Value`—Defines the value used in the comparisons. This is the right operand of the comparison. * `Operator`—Defines the `NumericalOperator` value that defines the boolean logic behind the left and right operand comparison. ## DateTime Filter Descriptor The `DateTimeFilterDescriptor` is a descriptor which filters by properties of the `System.DateTime` data type. The descriptor exposes the following properties: * `PropertyName`—Defines the name of the property that is used to retrieve the filter value. * `Value`—Defines the value used in the comparisons. This is the right operand of the comparison. * `Operator`—Defines the `NumericalOperator` value that defines the boolean logic behind the left and right operand comparison. ## TimeSpan Filter Descriptor The `TimeSpanFilterDescriptor` is a descriptor which filters by properties of the `System.TimeSpan` data type. The descriptor exposes the following properties: * `PropertyName`—Defines the name of the property that is used to retrieve the filter value. * `Value`—Defines the value used in the comparisons. This is the right operand of the comparison. * `Operator`—Defines the `NumericalOperator` value that defines the boolean logic behind the left and right operand comparison. ## Boolean Filter Descriptor The `BooleanFilterDescriptor` is a descriptor which filters by properties of the `System.Boolean` data type. The descriptor exposes the following properties: * `PropertyName`—Gets or sets the name of the property that is used to retrieve the filter value. * `Value`—Gets or sets the value used in the comparisons. This is the right operand of the comparison. ## Nested Property Text Filter Descriptor The `NestedPropertyTextFilterDescriptor` is a descriptor which filters the nested properties. The descriptor exposes the following properties: * `PropertyName`—Defines the name of the property that is used to retrieve the filter value. * `Operator`—Defines the `TextOperator` value that defines how the `Value` member is compared with each value from the items source. * `Value`—Defines the value used in the comparisons. This is the right operand of the comparison. * `IsCaseSensitive`—Defines a value that determines whether the text comparisons will be case-sensitive. The default value is `true`. ## Distinct Values Filter Descriptor The `DistinctValuesFilterDescriptor` is a descriptor which filters by distinct values. The descriptor exposes the following properties: * `PropertyName`—Defines the name of the property that is used to retrieve the filter value. * `Value`—Defines the value used in the comparisons. This is the right operand of the comparison. ## Composite Filter Descriptor The `CompositeFilterDescriptor` represents a special `FilterDescriptorBase` that stores an arbitrary number of other descriptors instances. The logical `AND` or `OR` operator is applied upon all composed filters to determine the result of the `PassesFilter` routine. ## Delegate Filter Descriptor The `DelegateFilterDescriptor` exposes the `Filter` property, which 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` by which you want to filter. Then, you need to add a `DelegateFilterDescriptor` to the `RadCollectionView.FilterDescriptors` collection and set its `Filter` property. ## See Also * [Grouping](https://www.telerik.com/maui-ui/documentation/controls/collectionview/grouping/overview) * [Sorting](https://www.telerik.com/maui-ui/documentation/controls/collectionview/sorting) * [Selection](https://www.telerik.com/maui-ui/documentation/controls/collectionview/selection) * [Commands](https://www.telerik.com/maui-ui/documentation/controls/collectionview/commands)