Here is a problem I encountered recently trying to perform a simple SQL operation using method syntax of Entity Framework. I had 2 IEnumerable<Object> datasets (dataset1 and dataset2). I wanted to join them to obtain a third dataset without loosing dataset1 records not referencing dataset2 records. To put it simply, I needed a Left Join from dataset1 to dataset2. The syntax would be straightforward in SQL; it would go like that : SELECT D1.Id, D1.Whatever, D2.Id, D2.Something FROM dataset1 ......