Hi All!
While i was hacking into linq and played around with expression trees i wondered why the underneath expression cannot be converted to a System.Expression. Is there someone who can enlight me It kinda looks buggy to me. Especially when
the Expression<Func<bool,bool>> ok = param1 => param1 == false; is converted without any error at all. Only chaning the true into false raises the error.
Func<bool,bool> f1 = p1 => true; Func<bool,bool> f2 = p2 => p2 == true; Expression<Func<bool,bool>> ok = param1 => param1 == false; //Ok! Expression<Func<bool,bool>> error = param1 => param1 == true; //Compile error |
IT gives me the error
Error 1 The expression contains operations that cannot be translated to a System.Expressions.Expression
Any ideas on this
Regards,
Emile
UPDATE: Even stranger if you use MS samples on DLINQ (Sample3)
var q = from p in db.Products where p.UnitsInStock <= p.ReorderLevel && p.Discontinued == false select p;
Changes into
var q = from p in db.Products where p.UnitsInStock <= p.ReorderLevel && p.Discontinued == true select p;
It doesnt seem to compile anymore, but doing
var q = from p in db.Products where p.UnitsInStock <= p.ReorderLevel && p.Discontinued select p;
seems to work
Cannot convert to System.Expressions.Expression type ?
Timo van Noppen
This is an issue with the preview compiler. It has to do with how the current internal representation of C# code lines up with the new experimental expression tree generation. It is not easy to fix in a "shallow" way, so you're probably not going to see it mended until the "real" (product) compiler revs up to deal with LINQ.
Luckily you have a workaround right there (since comparing with true is redundant except for readability), so hopefully you or others don't get blocked on it.
Thanks again!
Mads