ISupportIncrementalLoading interface (Windows)

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Specifies a calling contract for collection views that support incremental loading.

Syntax


public interface ISupportIncrementalLoading

Attributes

GuidAttribute("7f5ee992-7694-4e6c-a51b-e34bf43de743")
VersionAttribute(NTDDI_WIN8)
WebHostHiddenAttribute()

Members

The ISupportIncrementalLoading interface has these types of members:

Methods
Properties

Methods

The ISupportIncrementalLoading interface has these methods. It also inherits methods from the Object class.

Method	Description
LoadMoreItemsAsync	Initializes incremental loading from the view.

Properties

The ISupportIncrementalLoading interface has these properties.

Property	Access type	Description
HasMoreItems	Read-only	Gets a sentinel value that supports incremental loading implementations.

Examples

The following code example demonstrates how to implement this interface. For the complete code listing, see the XAML data Binding sample.

C++


#region ISupportIncrementalLoading

public bool HasMoreItems
{
    get { return HasMoreItemsOverride(); }
}

public Windows.Foundation.IAsyncOperation<LoadMoreItemsResult> LoadMoreItemsAsync(uint count)
{
    if (_busy)
    {
        throw new InvalidOperationException("Only one operation in flight at a time");
    }

    _busy = true;

    return AsyncInfo.Run((c) => LoadMoreItemsAsync(c, count));
}

#endregion 

#region INotifyCollectionChanged

public event NotifyCollectionChangedEventHandler CollectionChanged;

#endregion 

#region Private methods

async Task<LoadMoreItemsResult> LoadMoreItemsAsync(CancellationToken c, uint count)
{
    try
    {
        var items = await LoadMoreItemsOverrideAsync(c, count);
        var baseIndex = _storage.Count;

        _storage.AddRange(items);

        // Now notify of the new items
        NotifyOfInsertedItems(baseIndex, items.Count);

        return new LoadMoreItemsResult { Count = (uint)items.Count };
    }
    finally
    {
        _busy = false;
    }
}

void NotifyOfInsertedItems(int baseIndex, int count)
{
    if (CollectionChanged == null)
    {
        return;
    }

    for (int i = 0; i < count; i++)
    {
        var args = new NotifyCollectionChangedEventArgs(NotifyCollectionChangedAction.Add, _storage[i + baseIndex], i + baseIndex);
        CollectionChanged(this, args);
    }
}

#endregion

#region Overridable methods

protected abstract Task<IList<object>> LoadMoreItemsOverrideAsync(CancellationToken c, uint count);
protected abstract bool HasMoreItemsOverride();

#endregion 

#region State

List<object> _storage = new List<object>();
bool _busy = false;

#endregion

Requirements

Minimum supported client	Windows 8
Minimum supported server	Windows Server 2012
Namespace	Windows.UI.Xaml.Data Windows::UI::Xaml::Data [C++]
Metadata	Windows.winmd

ISupportIncrementalLoading interface