If you need to use the new LeftJoin/RightJoin operators, create an EF Core connection instead of a LINQ-to-SQL connection.

Note that LeftJoin/RightJoin operators are redundant noise in LINQ if a foreign key constraint exists. Instead, do this:

from p in Purchases
select new { p.Description, p.Customer.Name }

LINQ-to-SQL will automatically translate this into a LEFT OUTER JOIN if the CustomerID column in Purchases is nullable:

SELECT [t0].[Description], [t1].[Name]
FROM [Purchase] AS [t0]
LEFT OUTER JOIN [Customer] AS [t1] ON [t1].[ID] = [t0].[CustomerID]

Much easier than joining manually.

Re TagWith

I had previously changed a query to EF in order to use TagWith, so I tried switching back to Linq2Sql to try this out and got a few runtime errors.

An example using the NorthWind Database is

this.CurrentProductList.TagWith("CurrentProductList").Dump();

which throws InvalidOperationException: Sequence contains more than one element

The Sql tab shows

-- CurrentProductList

SELECT NULL AS [EMPTY]
GO

SELECT [t0].[ProductID], [t0].[ProductName]
FROM [Current Product List] AS [t0]

Also, can you add TagWithCallSite as well? (I know it should be trivial to write my own extension method, but I'm not sure how to add it to My Extensions without interfering with non-linq2sql query)

@JoeAlbahari said:
Thanks - this is now fixed, and TagWithCallSite has been added.

Thanks again