Performance
Query plans are reused more often by specifically defining text parameter lengths (when connecting to SQL 2005 or later)
Identity cache lookups for primary key with single result now includes query.Where(predicate).Single/SingleOrDefault/First/FirstOrDefault
Reduced query execution overhead when DataLoadOptions specified (cache lookup considers DataLoadOptions value equivalency)
Usability
ITable
Contains with enums automatically casts to int or string depending on column type
Associations can now specify non-primary-key columns on the other end of the association for updates
Support list initialization syntax for queries
LinqDataSource now supports inherited entities
LinqDataSource support for ASP.NET query extenders added
Query stability
Contains now detects self-referencing IQueryable and doesn’t cause a stack overflow
Skip(0) no longer prevents eager loading
GetCommand operates within SQL Compact transactions
Exposing Link
Compiled queries now correctly detect a change in mapping source and throw
String.StartsWith, EndsWith and Contains now correctly handles ~ in the search string (regular & compiled queries)
Now detects multiple active result sets (MARS) better
Associations are properly created between entities when using eager loading with Table-Valued Functions (TVFs)
Queries that contain sub-queries with scalar projections now work better
Update stability
SubmitChanges no longer silently consumes transaction rollback exceptions
SubmitChanges deals with timestamps in a change conflict scenario properly
IsDbGenerated now honors renamed properties that don’t match underlying column name
Server-generated columns and SQL replication/triggers now work instead of throwing SQL exception
Improved binding support with the MVC model binder
General stability
Binary types equate correctly after deserialization
EntitySet.ListChanged fired when adding items to an unloaded entity set
Dispose our connections upon context disposal (ones passed in are untouched)
Database control
DeleteDatabase no longer fails with case-sensitive database servers
SQL Metal
Foreign key property setter now checks all affected associations not just the first
Improved error handling when primary key type not supported
Now skips stored procedures containing table-valued parameters instead of aborting process
Can now be used against connections that use AttachDbFilename syntax
No longer crashes when unexpected data types are encountered
LINQ to SQL class designer
Now handles a single anonymously named column in SQL result set
Improved error message for associations to nullable unique columns
No longer fails when using clauses are added to the partial user class
VarChar(1) now correctly maps to string and not char
Decimal precision and scale are now emitted correctly in the DbType attributes for stored procedures & computed columns
Foreign key changes will be picked up when bringing tables back into the designer without a restart
Can edit the return value type of unidentified stored procedure types
Stored procedure generated classes do not localize the word “Result” in the class name
Opening a DBML file no longer causes it to be checked out of source control
Changing a FK for a table and re-dragging it to the designer surface will show new FK’s
Code generation (SQL Metal + LINQ to SQL class designer)
Stored procedures using original values now compiles when the entity and context namespaces differ
Virtual internal now generates correct syntax
Mapping attributes are now fully qualified to prevent conflicts with user types
KnownTypeAttributes are now emitted for DataContractSerializer with inheritance
Delay-loaded foreign keys now have the correct, compilable, code generated
Using stored procedures with concurrency no longer gets confused if entities in different namespace to context
ForeignKeyReferenceAlreadyHasValueException is now thrown if any association is loaded not just the first
Potentially breaking changes
We worked very hard to avoid breaking changes but of course any potential bug fix is a breaking change if your application was depending on the wrong behavior. The ones I specifically want to call out are:
Skip(0) is no longer a no-op
The special-casing of 0 for Skip to be a no-op was causing some subtle issues such as eager loading to fail and we took the decision to stop special casing this. This means if you had syntax that was invalid for a Skip greater than 0 it will now also be invalid for skip with a 0. This makes more sense and means your app would break on the first page now instead of subtlety breaking on the second page. Fail fast :)
ForeignKeyReferenceAlreadyHasValue exception
If you are getting this exception where you weren’t previously it means you have an underlying foreign key with multiple associations based on it and you are trying to change the underlying foreign key even though we have associations loaded.Best thing to do here is to set the associations themselves and if you can’t do that make sure they aren’t loaded when you want to set the foreign key to avoid inconsistencies.
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