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Entity Framework Caching Issue

I am new to Entity Framework.

I have get to some values in my database using EF. It returns perfectly, and the values are shown in labels. But When I delete all values in my table (without using EF), the EF query is returning my old values. I know the EF stores the values in cache and returns the cached data for subsequent runs. Is this correct?

So how can I solve the problem when I have deleted all values in my database, but EF returns the old values?

Edit:

Now i used datamodel.SaveChanges(). But now also it's returning the same old values.

My sample query is look like below:

SchoolBriefcaseEntities datamodel = new SchoolBriefcaseEntities();
datamodel.SaveChanges();
List<Compliance> compliance=new List<Compliance>();
IList<ComplianceModel> complianceModel;
if (HttpContext.Current.User.IsInRole("SuperAdmin"))
{
    compliance = datamodel.Compliances.Where(c => c.School.DistrictId == districtId).ToList();
}
like image 837
Ramesh Rajendran Avatar asked Apr 05 '13 08:04

Ramesh Rajendran


People also ask

Does Entity Framework cache data?

Entity Framework has the following forms of caching built-in: Object caching – the ObjectStateManager built into an ObjectContext instance keeps track in memory of the objects that have been retrieved using that instance. This is also known as first-level cache.

Does Entity Framework cache results?

The DbContext in Entity Framework 6 automatically caches data that it retrieves from your database. This is useful, but sometimes data changes outside your context (perhaps by another user) and you end up with stale data.

Does EF core cache data by default?

The Cache: The memory cache is used by default.

What is entity cache?

Entity cache is provided by EclipseLink ORM framework. It stores recently read or written entity instance in memory, which minimizes database access and improves the application performance. Entity cache is used only when you retrieve entities by ID, so queries by other attributes still run on the database.


9 Answers

If you know that changes happened outside of EF and want to refresh your ctxt for a specific entity, you can call ObjectContext.Refresh

datamodel.Refresh(RefreshMode.StoreWins, orders);

If this seems like it will be a common occurance, you should disable object caching in your queries:

SchoolBriefcaseEntities datamodel = new SchoolBriefcaseEntities();
datamodel.tblCities.MergeOption = MergeOption.NoTracking; 

or for to turn off object level caching for specific Entity,

Context.Set<Compliances>().AsNoTracking();
like image 64
Dave Alperovich Avatar answered Oct 01 '22 08:10

Dave Alperovich


EF will not load changes unless you re query the context. EF queries db and loads maps them into objects, it watches changes you perform on objects and not on the database. EF does not track changes made directly to database and it will never track.

You have loaded a List, that List is your cache in memory. Even calling Save Changes will not refresh. You will have to query the context once again, that is create new list.

To see changes You will have to execute following line once more,

datamodel.Compliances.Where(c => c.School.DistrictId == districtId).ToList()
like image 27
Akash Kava Avatar answered Oct 02 '22 08:10

Akash Kava


I think you should follow some of the other solutions here, but it seems like you're wanting to clear the cache. You can achieve this by doing the following:

var count = datamodel.Compliances.Local.Count; // number of items in cache (ex. 30)

datamodel.Compliances.Local.ToList().ForEach(c => {
    datamodel.Entry(c).State = EntityState.Detached;
});

count = datamodel.Compliances.Local.Count; // 0
like image 43
David Sherret Avatar answered Oct 01 '22 08:10

David Sherret


I recommend you to use some MergeOption to all EntitieSet after create the context, like this:

var objSetProps = ctx.GetType().GetProperties().Where(prop => prop.PropertyType.IsGenericType && prop.PropertyType.GetGenericTypeDefinition() == typeof(ObjectSet<>));
foreach (PropertyInfo objSetProp in objSetProps)
{
    ObjectQuery objSet = (ObjectQuery)objSetProp.GetValue(ctx, BindingFlags.GetProperty, null, null, null);
    objSet.MergeOption = MergeOption.PreserveChanges;
}

Read about the MergeOption here: http://msdn.microsoft.com/en-us/library/system.data.objects.mergeoption.aspx Your will use NoTracking, I think.

If you want to CLEAR the "cached" entities, detaching it.

var entidades = Ctx.ObjectStateManager.GetObjectStateEntries(EntityState.Added | EntityState.Deleted | EntityState.Modified | EntityState.Unchanged);
foreach (var objectStateEntry in entidades)
    Ctx.Detach(objectStateEntry.Entity);

Where Ctx are my Context.

like image 35
Tiago Gouvêa Avatar answered Oct 03 '22 08:10

Tiago Gouvêa


Below code helped my object to be refreshed with fresh database values. The Entry(object).Reload() command forces the object to recall database values

GM_MEMBERS member = DatabaseObjectContext.GM_MEMBERS.FirstOrDefault(p => p.Username == username && p.ApplicationName == this.ApplicationName);
DatabaseObjectContext.Entry(member).Reload();
like image 42
HGMamaci Avatar answered Oct 03 '22 08:10

HGMamaci


Firstly I would not suggest modifying the database external to your system unless you are only doing testing and development.

The EF DbContext contains an IDisposable interface. To release any cached data either make the Dispose calls manually or place your Database Object inside a using block.

        using (SchoolBriefcaseEntities datamodel = new SchoolBriefcaseEntities())
        {
            List<Compliance> compliance = new List<Compliance>();
            IList<ComplianceModel> complianceModel;
            if (HttpContext.Current.User.IsInRole("SuperAdmin"))
            {
                compliance = datamodel.Compliances.Where(c => c.School.DistrictId == districtId).ToList();
            }
        }

This will make sure the context is cleared and recreated the next time it is used. Make sure to do this for all your calls and not just the one you are having issues with.

like image 41
Brian from state farm Avatar answered Oct 03 '22 08:10

Brian from state farm


I suspect that the underlying problem here is that your DbContext is hanging around too long. I can tell from the fact that you are using HttpContext that you have a web application, and General guidelines when working with DbContext include

When working with Web applications, use a context instance per request.

If you are using MVC you could use the Dispose pattern in your controller like this:

public class EmployeeController : Controller
{
    private EmployeeContext _context;

    public EmployeeController()
    {
        _context = new EmployeeContext();
    }

    public ActionResult Index()
    {
        return View(_context.Employees.ToList());
    }

    protected override void Dispose(bool disposing)
    {
        if (disposing)
        {
            _context.Dispose();
        }
        base.Dispose(disposing);
    }
}

But you really ought to be looking at dependency injection to manage the DbContext lifetime

like image 26
Colin Avatar answered Oct 02 '22 08:10

Colin


I think what you need is GetDatabaseValues(). It is used like:

context.Entry(/*your entry*/).GetDatabaseValues();

Information below is from msdn:

The current values are the values that the properties of the entity currently contain. The original values are the values that were read from the database when the entity was queried. The database values are the values as they are currently stored in the database. Getting the database values is useful when the values in the database may have changed since the entity was queried such as when a concurrent edit to the database has been made by another user.

like image 33
Adil Mammadov Avatar answered Sep 30 '22 08:09

Adil Mammadov


Couple things you can do.

  1. Use a new context. The cached entities are stored in the context. Using a new context prevents it from using the cache.
  2. If you really want a global/long lasting context, you have two sub options: a.) always call the Reload method. db.Entry(entity).Reload() ... this forces the context to reload that entity. b.) use a SqlDependency object to detect when records change and reload the entities as needed. https://code.msdn.microsoft.com/How-to-use-SqlDependency-5c0da0b3
like image 35
Marc Johnston Avatar answered Oct 01 '22 08:10

Marc Johnston