Why does LINQ-to-SQL generate this SQL statement for a comparison - linq

Question

if I have a LINQ to SQL query like this:
var query = from x in db.XTable
select x.y == 123; // the y column is nullable!
List<bool> list = query.ToList();
it will generate a SQL statement that will contain this:
(CASE
WHEN [t0].[y] = 123 THEN 1
WHEN NOT ([t0].[y] = 123) THEN 0
ELSE NULL
END)
which will throw an error cause null could not get assigned to bool. I know why this happens (because a comparison in SQL with null is always false) but I don't know why LINQ to SQL does not use a stetement like this:
(CASE
WHEN [t0].[y] = 123 THEN 1
ELSE 0
END)
which would work.
Can I push LINQ to SQL to do this?

Answer 1

Probably, as you state, because you must think the SQL way with linq to sql, not the object way...
It might be considered as a bug or as a feature, by the way...
Especially with null values.
For example, concatenation of nullable string is different in linq to sql and linq to objects.
Assuming a and b are strings :
from n in db
select n.a + n.b
in linq to sql, if a is null and b is not, a + b = null
in linq to object if a is null anb b is not a + b = b
to get the same result in linq to sql, you'll have to use the coalesce operator select (a ?? string.Empty) + b
Anyway, you can either return a list of Nullable<bool> and a list of bool which would be :
from x in db.XTable
select x.y != null && x.y == 123
or
from x in db.XTable
select (x.y ?? 0) == 123
But to get what you want in linq to objects, you would have to do
from x in db.XTable.ToList()
select (x.y== null ? (bool?)null : x.y== 123))
EDIT
This might change in future versions (not sure if the given case will be included)