public class AClass : MonoBehaviour {

      // Use this for initialization
    void Start() {
        GameObject go = GameObject.Find("111");
        go.SendMessage("ObjMethode", new AClassExt { a = 2, b = gameObject});
    }
    public void ObjMethode(AClassExt _a)
    {
        Debug.Log(_a);
        Debug.Log(_a.a);
        Debug.Log(_a.b);
    }
}

public class AClassExt
{
    public int a;
    public GameObject b;
    
}