The long-awaited FullJoin for LINQ may appear in .NET 11
The .NET community is discussing the addition of a full-fledged full outer join to LINQ — the API has already been provisionally approved, but not yet implemented in the SDK and Entity Framework.
The new FullJoin method will allow data from both sides to be merged without losing elements, including in cases where there are no matches, which will close a long-standing gap in collections.