Serialization of Entity Framework proxy classes with Newtonsoft.Json fails with error that the object is disposed

Question

I've got an issue with serializing proxy classes with lazy loaded navigation properties. The error which I catch looks like this:

ObjectDisposedException: The ObjectContext instance has been disposed and can no longer be used for operations that require a connection.

The serialization fails when Newtonsoft.Json tries to do it:

JsonConvert.SerializeObject(objectGraph, _settings)

For example, the objectGraph is something like:

class Locations {
    public virtual ICollection<Department> Departments;
}

And Department property cannot be loaded because the context is already disposed.

Question:

How can I prevent loading of lazy loaded properties by the JSON serializer?

I tried to use #1 contract resolver, #2 type converter but they didn't help. It seems like the object loaded fully before apply those resolvers or converters. I suppose there should be some way to prevent from loading lazy properties.

Any ideas?

For those who is interested in the layout class code: git repo.

Can you add the code you pass data into JsonConverter? is it a Queryable or a list of entities? — Khai Nguyen
– Khai Nguyen, Commented Oct 10, 2018 at 8:39
It's just entity. I'm not passing directly. I've attached the layout through log4net configuration. type converters or contract resolvers are set to Json.NET in a standard way. Later in the code I'm calling log.Debug(entity). This is as simple as this. If time allows I try to simulate the issue on small project later. — Alexander Goida
– Alexander Goida, Commented Oct 10, 2018 at 8:47

RedFox · Accepted Answer · 2018-10-10 09:12:54Z

1

Have you tried using [yourQuery].AsNoTracking().FirstOrDefault() when querying the data from the Database.

You will then get the "real" object instead of a proxy object(https://stackoverflow.com/a/13077670/8336973).

When no tracking is active the lazy loading will not happen and everything that is not loaded will be NULL and not cause the ObjectDisposedException.

answered Oct 10, 2018 at 9:12

RedFox

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2 Comments

Alexander Goida Over a year ago

This is impossible unfortunately. The idea is that no code changes should be done in the way how production code is working. Only logging should be added. So I cannot change the way, how data is queried. But I've got a workaround by using a projections for logging. Instead of passing a proxy, I pass an anonymous object new { id = entity.Id, depIds = entity.Deps.select(d => d.Id).AsArray() } where I build a new object without lazy loading.

RedFox Over a year ago

The only other thing that came to my mind was using the DBContext context.Entry(entity).CurrentValues.ToObject(), but then you would need the DBContext and I'm afraid you don't have it, since you're getting the ObjectDisposedException. So I think using the anonymous object or mapping the proxy to another type (with AutoMapper) is the best solution :)

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