Is LeftJoin extension method supported?

pb_ · July 14

I'm running a simple query using .NET 10 and C# statement in one of my local dbs, the query is meant to join two tables using left join I get an error stating "Query Operator "LeftJoin" not supported"?

Wasn't LinqPad 9 supposed to support .NET 10 and C# 14?

JoeAlbahari · July 16

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.

JoeAlbahari · July 16

I've included LeftJoin/RightJoin support in the new LINQ-to-SQL drop in 9.10.7, so if you still want to use that in LINQ-to-SQL, you now can.

Enhanced LINQ-to-SQL features

Support for modern column types

DateOnly / TimeOnly (can be disabled on the Options tab)
SqlGeometry, SqlGeography and SqlHierarchyId
JSON and Vector (SQL Server 2025)

The SqlMethods class includes static methods to operate on JSON/Vector columns, such as JsonValue, JsonContains and VectorDistance.

Additional query operators

Order, OrderDescending
LeftJoin / RightJoin
CountBy, MinBy, MaxBy, DistinctBy, UnionBy, ExceptBy, IntersectBy
ElementAt, ElementAtOrDefault
Last, LastOrDefault
Reverse, Shuffle

Bulk operations and query shaping

ExecuteUpdate / ExecuteDelete perform set-based updates and deletes in a single round-trip without loading entities (same semantics as EF Core).
string.Join over a grouping is translated to SQL Server's STRING_AGG function.
TagWith annotates the generated SQL with a comment.
WithQueryHints injects query hints such as OPTIMIZE FOR UNKNOWN.

Support for Microsoft.Data.SqlClient

Microsoft.Data.SqlClient is used by default for new connections.
System.Data.SqlClient is supported via a checkbox in the Options tab.

sgmoore · July 16

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 · July 17

Thanks - this is now fixed, and TagWithCallSite has been added.

sgmoore · July 17

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

Thanks again

pb_ · July 24

Thanks @JoeAlbahari