/// <summary>
/// Create an instance from a specified change set provider and a collection touched strategy
/// </summary>
/// <typeparam name="TItem"></typeparam>
/// <param name="provider"></param>
/// <param name="collectionTouchedStrategy"></param>
/// <returns></returns>
///
public static ReadOnlyCollectionFromBackingStore <TItem> Create <TItem>(IChangeSetPagedDataProvider <TItem> provider, ICollectionItemTouchedStrategy collectionTouchedStrategy = null) where TItem : class
{
// create a backing store...
var backingStore = new SimpleBackingStoreCollection <TItem>(provider);
return(Create(backingStore, collectionTouchedStrategy));
}
/// <summary>
/// Create a collection
/// </summary>
/// <param name="changeSetProvider"></param>
/// <param name="scheduler">The scheduler on which data set changes are to be observed</param>
public SimpleBackingStoreCollection(IChangeSetPagedDataProvider <TItem> changeSetProvider, IScheduler scheduler = null)
{
Guard.NotNull(changeSetProvider);
// record the change set provider
_changeSetProvider = changeSetProvider;
// bind to the backing collection
_backingCollection = new ObservableCollectionExtended <TItem>();
_subscriptionDisposable.Disposable = changeSetProvider.Changes.
ObserveOn(scheduler ?? RxApp.MainThreadScheduler).
Bind(_backingCollection).
Subscribe();
}
/// <summary>
/// Create an enumeration of offsets required to read up to a specified offset.
/// </summary>
/// <typeparam name="TResultItem"></typeparam>
/// <param name="changeSetProvider"></param>
/// <param name="total"></param>
/// <param name="offset"></param>
/// <returns></returns>
public static IEnumerable <int> CreateOffsetsUpTo <TResultItem>(this IChangeSetPagedDataProvider <TResultItem> changeSetProvider, int?total, int offset)
{
var maxPageSize = changeSetProvider.MaxPageSize;
if (maxPageSize != int.MaxValue)
{
// at most a single read
if (!total.HasValue || offset < total)
{
yield return(offset);
}
{
var alignedOffset = ((int)Math.Round(((float)offset) / maxPageSize)) * maxPageSize;
if (!total.HasValue || offset < total)
{
while (alignedOffset < offset)
{
yield return(alignedOffset);
alignedOffset += maxPageSize;
}
}
}
}
else
{
if (!total.HasValue || offset < total)
{
yield return(offset);
}
{
if (total.HasValue)
{
yield return(Math.Min(offset, total.Value));
}
else
{
yield return(offset);
}
}
}
}
