.NET MAUI CollectionView LoadOnDemand Collection
To load items on demand, you can use the RadCollectionView.LoadOnDemandCollection and set it as an ItemsSource for the CollectionView.
The LoadOnDemandCollection is a generic type, so you need to point the type of objects it will contain. The type extends the ObservableCollection<T> class and expects a Func<CancellationToken, IEnumerable> in the constructor.
Example
The following example demonstrates a simple setup that shows how to use the collection:
1. Create a sample model:
public class Person
{
public string Name { get; set; }
public int Age { get; set; }
public Gender Gender { get; set; }
}
2. Define the CollectionView control:
<telerik:RadCollectionView ItemsSource="{Binding Items}"
DisplayMemberPath="Name"
LoadOnDemandBufferItemsCount="8"
IsLoadOnDemandEnabled="True">
<telerik:RadCollectionView.BindingContext>
<local:LoadOnDemandCollectionViewModel />
</telerik:RadCollectionView.BindingContext>
</telerik:RadCollectionView>
3. Add the telerik namespace:
xmlns:telerik="http://schemas.telerik.com/2022/xaml/maui"
4. Create a ViewModel and use the LoadOnDemandCollection as a type of the property bound to the RadCollectionView.ItemsSource:
public class LoadOnDemandCollectionViewModel : NotifyPropertyChangedBase
{
public LoadOnDemandCollectionViewModel()
{
this.Items = new LoadOnDemandCollection<Person>(this.LoadMoreItems);
for (int i = 0; i < 20; i++)
{
this.Items.Add(new Person { Name = "Person " + i, Age = i + 10 });
}
}
public LoadOnDemandCollection<Person> Items { get; set; }
private IEnumerable LoadMoreItems(CancellationToken cancellationToken)
{
List<Person> newItems = new List<Person>();
int count = this.Items.Count;
try
{
Thread.Sleep(2500);
for (int i = 0; i < 10; i++)
{
newItems.Add(new Person { Name = $"Loaded item: Person {count + i}", Age = count + i + 10 });
}
return newItems;
}
catch (Exception)
{
return null;
}
}
}
This is the result:
For a runnable example demonstrating the CollectionView LoadOnDemand Collection, see the SDKBrowser Demo Application and go to CollectionView > Load On Demand category.