linq subquery returning null
linq, linq-to-sql
Solution
I wonder if the compiler is inferring HasHomeChildrenWithFoo to be bool, but then actually casting to a nullable bool (thus messing up your SingleOrDefault call). At any rate, I'd be willing to bet you could fix it with a cast to a nullable type in that final select which you can then manually default to false when null. It'd probably make the error go away, but it's kind of a brute-force kludge.
var parentList = from p in Parents
select new ParentObject
{
ParentId = p.ParentId,
HasHomeChildren = p.Children.Any(c => c.Location == "Home"),
HasHomeChildrenWithFoo = (from c in p.Children where c.Location == "Home" select (bool?)c.HasFoo) ?? false)
}
Problem
I have an odd linq subquery issue. Given the following data structure: ``` Parents Children ------- -------- Id Id ParentId Location HasFoo ``` (obviously this is not the real structure, but it's close enough for this example) I'm able to run this query and get a desired result: ``` bool b = (from p in Parents from c in Children where p.Id == 1 && c.ParentId == p.Id && c.Location == "Home" select c.HasFoo).SingleOrDefault(); ``` So if there is a child that has the Location "Home" for a Parent of Id 1, I will get that Child's "HasFoo" value, otherwise, I'll get false, which is the "default" value for a bool. However, if I try and write the query so I have a list of Parent objects, like so: ``` var parentList = from p in Parents select new ParentObject { ParentId = p.ParentId, HasHomeChildren = p.Children.Count(c => c.Location == "Home") > 0, HasHomeChildrenWithFoo = (from c in p.Children where c.Location == "Home" select c.HasFoo).SingleOrDefault() } ``` I get the following error when iterating over the list: ``` The null value cannot be assigned to a member with type System.Boolean which is a non-nullable value type. ``` I don't see where this "null" value is coming from, however.