protected IAggregateFluent <TEntity> CreateAggregate(FilterDefinition <TEntity> filter, SortDefinition <TEntity> sort, ReadPreference readPreference = null)
{
IAggregateFluent <TEntity> fluent = IMongoCollectionExtensions.Aggregate(this.GetCollection(readPreference), null).Match(filter);
if (sort != null)
{
fluent = fluent.Sort(sort);
}
return(fluent);
}