c# - cannot access a disposed object UserManager in asp.net mvc core -

i have following code in service should create usermanager instance

public class subscriptionservice : isubscriptionservice {      private usermanager<applicationuser> usermanager;     public usermanager<applicationuser> usermanager     {                 {             return usermanager;            }         private set { usermanager = value; }     }      public subscriptionservice(         usermanager<applicationuser> usermanager,            stripecustomerservice customerservice,          stripesubscriptionservice subscriptionservice)     {         this.usermanager = usermanager;         this.customerservice = customerservice;         this.subscriptionservice = subscriptionservice;     }      public subscriptionservice(usermanager<applicationuser> usermanager)     {         this.usermanager = usermanager;     } 

when usermanager called first time inside class, works second call returns error "cannot access disposed object usermanager"

i'm consuming subscriptionservice class in controller with:

public isubscriptionservice subscriptionservice {         {         return subscriptionservice ?? new subscriptionservice(_usermanager);     }     private set     {         subscriptionservice = value;     } } 

can point me i'm wrong , how fix it?

i'm using asp.net core 1.0

edit: here's user manager inspected right after first execution in function