سلام دوستان

من متوجه این خطا نمیشم چیه؟   موقعی که کد db.savechnage(); میخواد اجرا بشه این خطا رو میده

The context cannot be used while the model is being created.
 This exception may be thrown if the context is used inside the OnModelCreating method or 
if the same context instance is accessed by multiple threads concurrently. Note that instance