/// <summary>
/// This can be called to prepare a range of data prior to usage.
/// </summary>
/// <param name="index"></param>
/// <param name="take"></param>
public void PreloadRangeAsync(int index, int take)
{
if (index >= TotalItems())
{
return;
}
//don't start preloading new data until the previous data has been preloaded.
if (_donePreloadingDataEvent != null)
{
_donePreloadingDataEvent.WaitOne();
}
// if we're at the end of the data set, don't pick a range that's out of bounds.
var numberToTake = Math.Min(take, TotalItems() - index);
var range = CachedData.ToList().GetRange(index, numberToTake);
//if all values are already cached, return them
var firstDefaultIndex = range.FindIndex(s => s == default(S));
if (firstDefaultIndex == -1)
{
return;
}
_donePreloadingDataEvent = new ManualResetEvent(false);
ThreadPool.QueueUserWorkItem(AsyncDataLoadingHandler, new DataLoadRequest(index, numberToTake));
}
/// <summary>
/// Get a subset of the items.
/// </summary>
/// <param name="index">the index from which to start</param>
/// <param name="take">the number of items to pull out.</param>
/// <returns></returns>
public S[] GetRange(int index, int take)
{
//don't start preloading new data until the previous data has been preloaded.
//TODO allow for preloading multiple ranges at the same time.
if (_donePreloadingDataEvent != null)
{
_donePreloadingDataEvent.WaitOne();
}
if (index > TotalItems())
{
throw new ArgumentException(string.Format("Index of: {0} was greater than total items: {1}", index, TotalItems()));
}
if (take == 0)
{
return(new S[0]);
}
else if (take < 0)
{
throw new ArgumentException(string.Format("For index {0}, take had a value of {1}.", index, take));
}
// if we're at the end of the data set, don't pick a range that's out of bounds.
var numberToTake = Math.Min(take, TotalItems() - index);
var range = CachedData.ToList().GetRange(index, numberToTake);
//if all values are already cached, return them
var firstDefaultIndex = range.FindIndex(s => s == default(S));
if (firstDefaultIndex == -1)
{
return(range.ToArray());
}
LoadAsNeeded(range, index);
return(range.ToArray());
}