Sets - .NET SDK
New in version 10.2.0.
Overview
A Realm set, like the C#
HashSet<>,
is an implementation of
ICollection<>
and
IEnumerable<>.
It supports values of any
Realm type except collections.
To define a set, use a getter-only ISet<TValue> property, where TValue
is any of the supported types.
Deleting an object from the database will remove it from any sets
in which it existed. Therefore, a set of objects will never contain null objects.
However, sets of primitive types can contain null values. If you do not
want to allow null values in a set, then either use non-nullable types in
the set declaration (for example, use ISet<double> instead of
ISet<double?>). If you are using the older schema
type definition (your classes derive from the RealmObject base class),
or you do not have nullability enabled, you will need to use the
[Required] attribute if the set
contains nullable reference types, such as string or byte[].
Important
Not Supported with Sync
Local-only realms support collections of nullable (optional) values,
but Sync does not.
Set Types
The following code shows examples of set types:
public partial class Inventory : IRealmObject { // A Set can contain any Realm-supported type, including // objects that inherit from RealmObject public ISet<Plant> PlantSet { get; } public ISet<double> DoubleSet { get; } // Nullable types are supported in local-only // Realms, but not with Sync public ISet<int?> NullableIntsSet { get; } public ISet<string> RequiredStrings { get; } }
Usage Example
The following code shows how to create, write to, and read from Sets.
var inventory = new Inventory(); inventory.PlantSet.Add(new Plant() { Name = "Prickly Pear" }); inventory.DoubleSet.Add(123.45); realm.Write(() => { realm.Add<Inventory>(inventory); }); // convert the Plant Set to an IQueryable and apply a filter var pricklyPear = inventory.PlantSet.AsRealmQueryable() .Where(p => p.Name == "Prickly Pear"); // Alternatively, apply a filter directly on the Plant Set var pricklyPearPlants = inventory.PlantSet .Filter("Name == 'Prickly Pear'"); // Find all Inventory items that have at least one value in their // DoubleSet that is larger than 5 var moreThan100 = realm.All<Inventory>() .Filter("DoubleSet.@values > 100");
Watching For Changes
You can use the INotifyCollectionChanged.CollectionChanged event on a set to watch for changes to the set, and the INotifyPropertyChanged.PropertyChanged event to watch for changes to specific properties in the set.
In the following code example, we have a class with an
ISet<string> property named StringSet. We set up event
handlers for both the CollectionChanged and PropertyChanged events:
var stringSet = container.StringSet.AsRealmCollection(); stringSet.CollectionChanged += (sender, e) => { Console.WriteLine($"Set {sender} changed: {e.Action}"); }; stringSet.PropertyChanged += (sender, e) => { Console.WriteLine($"Property changed on {sender}: {e.PropertyName}"); };