public static IEnumerable <IGrouping <TKey, TSource> > IndexGroupBy <TKey, TSource>(this CSVDataSet <TSource> csvDataSet, Func <TSource, TKey> keySelector)
{
IndexManager <object, Segment> workingIndexManager = new IndexManager <object, Segment>();
string indexName = "TempGroup";
var innerEnumerable = csvDataSet.GetTypedEnumerable(1);
foreach (TSource row in innerEnumerable)
{
var key = keySelector(row);
Segment segment = csvDataSet.CurrentSegment;
workingIndexManager.AddMapForKey(indexName, key, segment);
}
IndexTable <object, Segment> indexTable = workingIndexManager.GetMap(indexName);
foreach (TKey key in indexTable.GetMapKeys())
{
var source = csvDataSet.GetIndexedTypedEnumerable(indexName, key, workingIndexManager);
yield return(new IndexGrouping <TKey, TSource>(key, source));
}
workingIndexManager = null;
}
