public Task <TSource> SingleAsync <TSource>(IQueryable <TSource> source, CancellationToken cancellationToken = default(CancellationToken)) => LinqExtensionMethods.SingleAsync(source, cancellationToken);
public Task <TSource> SingleAsync <TSource>(IQueryable <TSource> source, Expression <Func <TSource, bool> > predicate, CancellationToken cancellationToken = default(CancellationToken)) => LinqExtensionMethods.SingleAsync(source, predicate, cancellationToken);