Here is more information about the C and D options.
Option C acts as if the variable in the LINQ query is just like any
other database element. It generates A = B except for these special
cases:
X == null (literal only)
X != null (literal only)
With option C, LINQ statements that look like this:
.Where(customer => Customer.Representative == representative)
generate this in all cases:
Representative = @representative
Option D assume that the developer is aware of the value of the
variable and uses the variable contents to figure out whether to
generate an IS NULL clause. It generates A = B except in these
special cases:
X == null
X != null
X == nullVariable
X != nullVariable
Using:
.Where(customer => Customer.Representative == representative)
generate these depending on if representative is null:
Representative IS NULL
Representative = @representative
In support of option C:
-Consistent with Linq to SQL
-Consistent with Entity Framework
-Same result as if variable was an actual SQL variable.
-Might be difficult to see that an expression like c => a.X == b.Y is
going to be converted to a.X IS NULL just because b.Y is an in-memory
variable that is null.
In support of option D:
-NHibernate already does it this way.
-Developers seem to expect it. 3/3 of polled developers at my office
expected it (one very strongly so).
-The connect bug report expected it and gave many other examples of
people expecting it.
-If X == null is already special cased, it's a logical extension to
special case X == nullVariable.
-It is strange if X == Y is not the same as X == null when Y == null.
-Rarely does anyone actually need "= null" to evaluate to NULL. When
it does come up, it's usually desirable to have it converted to IS
NULL.
-llblgen's LINQ provider does it this way.
So, from the perspective of a programmer who's going to use the
system, I now prefer option D.
So my final vote is for A+D (change the equality part to convert == to
= directly, but leave the null variable handling alone).
I realized that it was silly to use "A,B,C,D" when it's really two
decisions. Sorry if that confused anyone. The options at this point
are:
A+C
A+D
B+C
B+D
Looking forward to hearing more people's views on this issue.
Patrick Earl
