entity framework to a list<>?

Question

i use entity framework and have the below code:

public class AdvPackageInfo
{
    private int PackageId;
    private string Caption;
    private int Duration;
    private int Count;
    private bool Enable;
    private float Price;
}


 AdvertismentAgancyEntities enn = new AdvertismentAgancyEntities();

 List<AdvPackageInfo> lst = (from s in enn.Tbl_AdvPackage select new AdvPackageInfo { }).ToList();

    repeater1.DataSource = lst;
    repeater1.DataBind();

but it works just 1 time and when my page load for the second time it fails in execution and raise NullReferenceException...!!

according to this pag : http://connect.microsoft.com/VisualStudio/feedback/details/663200/linq-to-entities-throws-nullreferenceexception-when-the-output-attribute-set-is-empty
it's dot net framework problem.

i try this code too :

var q = (from s in enn.AdvPackage select s).toList();

but it doesn't work either.

is there any better way to make a linq select to a list????

Isn't it possible that enn.Tbl_AdvPackage is null in the second call? (I'm trying to rule out the more plausible causes first) — SmartK8, Jan 19 '13 at 11:30
Can you paste the code inside your page? I think the problem is not entity framework but what append in your page after executing query. You use the same object? Are you disposing components after query execution? — Roberto Conte Rosito, Jan 19 '13 at 11:37
@SmartK8 : from first time to second time nothing change. by second time i means when i refresh the page. — maryam mohammadi, Jan 19 '13 at 11:51
@sprinter252 : i don't know which variable. it said just " Object reference not set to an instance of an object" nothing more. — maryam mohammadi, Jan 19 '13 at 11:53
As a side-issue - you are not seriously using a float for "price" are you? — flytzen, Jan 19 '13 at 22:45
@Frans while that was a good pick-up (vote-up), please be specific http://stackoverflow.com/a/1165788/201648. — Aaron Newton, Jan 20 '13 at 00:20
@maryammohammadi Which is nothing but saying that something is null. If you debug your code and hover over some variables one of them supposed to be null. Would be good to know, which. — Alexander Schmidt, Jan 20 '13 at 10:51

Eren Ersönmez · Accepted Answer · 2013-01-19T12:06:32.427

3

Instead of this line:

List<AdvPackageInfo> lst = 
    (from s in enn.Tbl_AdvPackage select new AdvPackageInfo { }).ToList();

You could do this:

var lst = new List<AdvPackageInfo>();
for (int i = 0; i < enn.Tbl_AdvPackage.Count(); i++)
    lst.Add(new AdvPackageInfo());

(Note that the suggested workaround in the MS Connect page is wrong. Using Enumerable.Repeat will create a list full of references to a single object)

Update per comment below: If you're just trying to load the datagrid, then you just need to retrieve the list as:

var lst = enn.Tbl_AdvPackage.ToList();

edited Jan 19 '13 at 12:06

answered Jan 19 '13 at 11:38

Eren Ersönmez

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thank u. it works for the error but there is another problem now! it returns empty records. i mean although there is 5 records of data it returns 5 empty records. i see 5 empty records in grid!! – maryam mohammadi Jan 19 '13 at 11:47
Then you haven't stated what you're trying to do very clearly. You're actually trying to just load the records, not create an empty object object for each record. Please see the update. – Eren Ersönmez Jan 19 '13 at 12:07

entity framework to a list<>?

1 Answers1