Why can't I cast in generic class in realm-dotnet?

Question

I use Realm dotnet. I wrote the generic class for any object.

It is my generic class.

public class Controller<T> where T : RealmObject, new()
{
    private Realm realm;
    public Controller()
    {
        this.realm = Realm.GetInstance();
    }

    public void Insert(T selfObj)
    {
        this.realm.Write(() => 
            {
                Debug.WriteLine(typeof(T)); // => "Country".


                // ERROR: System.InvalidCastException has been thrown Specified cast is not valid.
                var obj = this.realm.CreateObject<T>();

                // TODO: write later.
            }
    }
}

And model class is here.

public class Country : RealmObject
{
    public string Name { get; set; }
}

And, I called like this.

    var cc = new Controller<Country>();
    Country newCon = new Country()
    {
        Name = "Japan"  
    };

    var newCon2 = new Country()
    {
        Name = "Korea"  
    };

    cc.Insert(newCon);

The System.InvalidCastException has been thrown Specified cast is not valid. error occurred.

My Controller class already known T is Country object. Why realm.CreateObject<T>(); can't cast?

Could you tell me how to fix.

Answer 1

Update

The issue was resolved via email. The real class Country descends from an intermediate Model class which descends in turn from RealmObject .

Currently we don't support inheritance in this manner. It is documented in our help .

We are probably going to move to using an interface instead of base class. There is a git issue discussing this .

Original

Firstly, I can't reproduce your exception with the current 0.76.1 release of Realm.

Using standalone objects like this works to a point. We don't yet support standalone objects which have relationships to other objects (see this IList issue ).

One minor change to your code sample. To pass a RealmObject which is created standalone and copy it into a Realm, you can simply use Manage . eg:

public class Controller<T> where T : RealmObject, new()
{
    private Realm realm;
    public Controller()
    {
        this.realm = Realm.GetInstance();
    }

    public void Insert(T selfObj)
    {
        this.realm.Write(() => 
            {
                Debug.WriteLine(typeof(T)); // => "Country".

                this.realm.Manage<T>(selfObj);
            }
        );  // closing paren was missing above too
    }
}