System.InvalidCastException: 'Object cannot be cast from DBNull to other types.' asp.NET CORE

Question

when i try to run my solution roject i get this erro mesage on this line code

System.InvalidCastException: 'Object cannot be cast from DBNull to other types.'

 if (Convert.ToInt32(dr["Visitas"]) == null)
                        {
                            visitas = 0;
                        }