what's the catch (select new in LINQ vs simply filling the object)

Question

Hello everybody, can someone please explain the difference between these 2 pieces of code:

var temp = (from c in Context.SomeTable 
            select new SomeObject { name=c.Name, created = c.Created}).ToList();

and this :

var temp = (from c in Context.SomeTable select c);
foreach(SomeTable t in temp)
{
SomeObject so = new SomeObject();
so.name = t.Name;
so.created = t.Created;
}

SomeTable.Created is a nullable datetime type field in the database.

While the first piece throws an exception:

Sqldatetime overflow. must be between 1/1/1753 12:00:00 am and 12/31/9999 11:59:59 pm.

the second one works.

Thank You!

Answer 1

In the first code no c will be read from SomeTable or instance of SomeObject will be created until something enumerates temp.

The second this enumeration takes place.

Therefore I would expect there is an issue with the validity of Context.SomeTable when temp is enumerated in the first case.

Test this by changing the first block to:

var temp = (from c in Context.SomeTable 
            select new SomeObject { name=c.Name, created = c.Created}
           ).ToList();

which forces immediate enumeration.