// Called after a reset to figure out the new indexes for the selected items
private async Task RemapSelection()
{
ItemIndexRangeList oldSelection = selection;
ItemCacheManager <string> oldSelectionCache = selectionCache;
ItemIndexRangeList newSelection = new ItemIndexRangeList();
ItemCacheManager <string> newSelectionCache = new ItemCacheManager <string>(fetchSelectionDataCallback, 50, "newSelectionCache");
foreach (ItemIndexRange r in oldSelection)
{
IReadOnlyList <StorageFile> results = null;
int lastResultOffset = 0, lastResultsItemIndex = 0;
for (int i = 0; i < r.Length; i++)
{
int origIndex = r.FirstIndex + i;
string fileid = oldSelectionCache[origIndex];
bool matched = false;
// Optimization to be able to work in batches. Once we get a batch of files from the filesystem we use that to hunt
// for matches rather than having to go ask for the index of each file
if (results != null)
{
for (int j = lastResultOffset + 1; j < results.Count; j++)
{
if (results[j].FolderRelativeId == fileid)
{
lastResultOffset = j;
int itemIndex = lastResultsItemIndex + j;
newSelection.Add((uint)itemIndex, 1);
newSelectionCache[itemIndex] = oldSelectionCache[origIndex];
matched = true;
break;
}
}
}
if (!matched)
{
// Get a starting point for the index of the file
lastResultsItemIndex = (int)(await _queryResult.FindStartIndexAsync(fileid.Substring(fileid.LastIndexOf('\\') + 1)));
lastResultOffset = 0;
// Get the files at that point and see if the keys actually match
results = await _queryResult.GetFilesAsync((uint)lastResultsItemIndex, 50);
if (results[lastResultOffset].FolderRelativeId == fileid)
{
newSelection.Add((uint)lastResultsItemIndex, 1);
newSelectionCache[lastResultsItemIndex] = oldSelectionCache[origIndex];
}
else
{
// We can't find the item, so its no longer part of the selection
}
}
}
}
// Update the fields for the new selection
selection = newSelection;
selectionCache = newSelectionCache;
}