Webapi2返回ef对象

Question

I have a problem with entity framework object in a webapi project. Since 2-3 days ago everything works fine, but now, the api I call always return "Out of memory exception".

Initially I check for the classic "circular reference error" but is not the case.

In the webapi configuration I have this

config.Formatters.JsonFormatter.SerializerSettings.TypeNameHandling = TypeNameHandling.None;
        config.Formatters.JsonFormatter.SerializerSettings.Formatting = Formatting.None;
        config.Formatters.JsonFormatter.SerializerSettings.ReferenceLoopHandling = Newtonsoft.Json.ReferenceLoopHandling.Ignore;
        config.Formatters.JsonFormatter.SupportedMediaTypes.Add(new MediaTypeHeaderValue("application/json"));

And to return ef object I use function like this

public Contatti GetContatto([FromUri]int id)
    {
        var db=new WebEntities();
        return(db.Contatti.Single(x=>x.IDContatto == id));
    }

There's a way to return an ef object (with its subobject) in a json response with webapi2?

Answer 1

I didn't really look at the code you've posted when I commented on your question, but now that I did I have some remarks:

Always call dispose , do not wait for the GC to clear memory. Though the "Out of Memory" exception may not be caused by this particular method, it is possible that you are also not disposing other (large) objects, like images. So review your code and dispose objects where possible. Best way to prevent "Out of memory" exceptions.

    public Contatti GetContatto([FromUri]int id)
    {
        using(var db = new WebEntities())
        {
            return(db.Contatti.Single(x => x.IDContatto == id));
        }
    }

Is there a way to return an ef object (with its subobject) in a json response with webapi2?

Yes, but I would really recommend not to return EF objects but use DTO's instead. Saves a lot of trouble!

To return an EF object, you'd better unproxy the object first:

    protected internal T UnProxyItem<T>(T proxyObject) where T : class
    {
        var proxyCreationEnabled = this.Configuration.ProxyCreationEnabled;
        try
        {
            this.Configuration.ProxyCreationEnabled = false;
            return this.Entry(proxyObject).CurrentValues.ToObject() as T;
        }
        finally
        {
            this.Configuration.ProxyCreationEnabled = proxyCreationEnabled;
        }
    }