How do I clear tracked entities in entity framework

I am running some correction code that runs over a big pile of entities, as it progress its speed decreases, that is because the number of tracked entities in the context increase with each iteration, It can take long so I am saving changes at the end of each iteration. Each iteration is independent and does not change the previosuly loaded entities.

I know I can turn off change tracking but I do not want to, because it is not a bulk insert code, but loading the entities and calculating a few things and if the numbers are not correct set the new numbers and update/delete/create some additional entities. I know I can create a new DbContext for each iteration and probably that would run faster than doing all in the same instance, but I am thinking that there might be a better way.

So the question is; Is there a way of clearing the entities previously loaded in the db context?

Solution 1:

You can add a method to your DbContext or an extension method that uses the ChangeTracker to detach all the Added, Modified, and Deleted entities:

public void DetachAllEntities()
{
    var changedEntriesCopy = this.ChangeTracker.Entries()
        .Where(e => e.State == EntityState.Added ||
                    e.State == EntityState.Modified ||
                    e.State == EntityState.Deleted)
        .ToList();

    foreach (var entry in changedEntriesCopy)
        entry.State = EntityState.Detached;
}

Solution 2:

EntityFramework Core 5.0 introduced a new method to clear any tracked changes.

_context.ChangeTracker.Clear();

https://docs.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.changetracking.changetracker.clear?view=efcore-5.0

Solution 3:

1. Possibility: detach the entry

dbContext.Entry(entity).State = EntityState.Detached;

When you detach the entry the change tracker will stop tracking it (and should result in better performance)

See: http://msdn.microsoft.com/de-de/library/system.data.entitystate(v=vs.110).aspx

2. Possibility: work with your own Status field + disconnected contexts

Maybe you want to control the status of your entity independently so you can use disconnected graphs. Add a property for the entity status and transform this status into the dbContext.Entry(entity).State when performing operations (use a repository to do this)

public class Foo
{
    public EntityStatus EntityStatus { get; set; }
}

public enum EntityStatus
{
    Unmodified,
    Modified,
    Added
}

See following link for an example: https://www.safaribooksonline.com/library/view/programming-entity-framework/9781449331825/ch04s06.html

Solution 4:

I'm running a windows service that updates values every minute and I have had the same problem. I tried running @DavidSherrets solution but after a few hours this got slow as well. My solution was to simply create a new context like this for every new run. Simple but it works.

_dbContext = new DbContext();