“Cannot call methods on DateTime”, and other limitations

Question

Does anyone know of a definitive list of LINQ to SQL query limitations that are not trapped at compile time, along with (where possible) workarounds for the limitations?

Answer 1

LINQ is the language. LINQ-to-SQL compiles your LINQ command down into a SQL query. Thus, it is limited by the normal limitations of the TSQL syntax, or rather the items that can easily be converted into it.

As others have said, the lists of what you cannot do would be enormous. It is a much smaller list of what you can do. A general rule of thumb is to try to determine how the function you want to use would be converted into TSQL. If you have much trouble figuring it out, then don't use that function (or at least test it first).

But there is an easy work around to use LINQ commands that are not in LINQ-to-SQL. Separate the pure LINQ portions of your code from the LINQ-to-SQL portions. In other words, do the LINQ-to-SQL to pull the data in (with any functions you need that are available in LINQ-to_SQL), with the command to put it into an object (ToEnumerable, ToList, or others similar). This executes the query and pulls the data local. Now it is available for the full LINQ syntax.