CODEWITHSUNDEEP
c#asp.net-mvcentity-framework
DAK
DAK

Reputation: 1435

Entity Framework keeping track of changes

I'm new with MVC & Entity Framework and trying to track changes. Here is my code snippet:

string historyText = "<ul>";
ICollection<LookUp> oldPositions = fromDB.LookUps;

fromDB.LookUps.Clear();
IEnumerable<LookUp> allPositionTypes = lookUpRepository.GetByLookupTypeId(24);
foreach (var interest in chkPositionType)
{
    fromDB.LookUps.Add(allPositionTypes.Where(x => x.LookUpID == Convert.ToInt32(interest)).Single());
    if (!oldPositions.Contains(allPositionTypes.Where(x => x.LookUpID == Convert.ToInt32(interest)).Single()))
         historyText += "<li>" + "Position Type : <span class='history-old'> </span><span class='history-separator'>|</span><span class='history-new'>" + lkupRepo.GetByID(Convert.ToInt32(interest)).Name + "</span></li>";
}
historyText += "</ul>";

For some reason as soon as I clear Lookups, it sets oldPositions to null too. I would also like to know the ones I added new and those which were deleted but didn't add again. So basically need to track changes.

Is there any alternate way? If its better I can adopt it too.

Upvotes: 2

Views: 330

Answers (2)

deDogs
deDogs

Reputation: 739

I believe oldPositions is losing reference to fromDB.Lookups when calling the Clear() method.

ICollection oldPositions = fromDB.LookUps;

fromDB.LookUps.Clear();

oldPositions has a reference pointer to fromDB.LookUps collection. fromDB.LookUps collection references to other objects from elements are released, so oldPositions will be empty.

Upvotes: 0

humblelistener
humblelistener

Reputation: 1456

  1. change oldPosition to enumerate of the LookUp, like below
    var oldPositions = fromDB.LookUps.ToList();

  2. Remove fromDB.LookUps.Clear() and it should work.

Upvotes: 2

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