Which method has a better performance ?

Question

Hello !
I'm using entity framework , and I have several cases where I should run a query than return some parent items , and after I display these parents and the related children  in one report.
I want to know which of these methods have the better performance : ( or is there any other better method ??? )
Method1: (the childs collection are loaded later , using lazy loading)
Dim lista as IQueryable(Of MyObj) = (From t In context.MyObjs Where(..condition..) select t).Tolist
Method2:
Dim lista as IQueryable(Of MyObj) = (From t In context.MyObjs Where(..condition..) _
.Include(Function(t2) t2.Childs1) _
.Include(Function(t2) t2.Childs2) _
.Include(Function(t2) t2.Childs2.Child22) _
.Include(Function(t2) t2.Childs1.Childs11) _
.Include(Function(t2) t2.Childs1.Childs12) _
Select t).ToList
Method3:
Dim lista as IQueryable(Of MyObj)
Dim lst= (From t2 In context.MyObjs Where(..condition..) Select New with _
{ .Parent=t2
.ch1=t2.Childs1 _
.ch2=t2.Childs2 _
.ch21=t2.Childs2.Child21) _
.ch11=t2.Childs1.Childs11) _
.ch12= t2.Childs1.Childs12 _
).ToList
lista=lst.Select(Function(t2) t2.parent)
I noticed that the first method cause the report to open very slow. Also I read somewhere that Include() cause repeat of parent items?
But anyway I want a professional opinion in general for the three methods.
Thank you !

Answer 1

Hello,
As far as I know, the Entity Framework offers two ways to load related data after the fact. The first is called lazy loading and, with the appropriate settings, it happens automatically. In your case, your first method uses the last loading, while the second
and third are the same actually, both of them are Eager Loading. (In VB, if you could check use code as “DbContext.Database.Log = Sub(val) Diagnostics.Trace.WriteLine(val)” to see the actually generated sql statement, you could see the third and second query
would generate a join syntax). Since you mentions, the lazy loading way is low performance, you could use either the second or third one.
>>Also I read somewhere that Include() cause repeat of parent items?
For this, nor sure if you worry it would firstly use lazy loading and then use eager loading, however, in my test, I do not see this behavior, the Entity Framework seems to be smart enough to use one mode to load data at the same time. Or you could disable
its lazy loading when using eager loading:
context.ContextOptions.LazyLoadingEnabled = false
Regards.
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