c# - Update Many to Many Entity Framework. Cannot remove from many to many table -

there many many relationship between user , roles. can add role many many table, cannot remove it, not give me error don't remove roles remove. try found. here code.

public user update(user entity)     {         using (var context = new enersysentities())         {              var user = context.users.single(u => u.user_id == entity.user_id);              //all roles in data base             list<role> rolealreadyassigned = getbyid(entity.user_id).roles.tolist();              //roles remove             list<role> rolestoremove =                 rolealreadyassigned.where(x => entity.roles.all(y => y.role_id != x.role_id)).tolist();              //roles add             list<role> rolestoadd =                 entity.roles.where(x => rolealreadyassigned.all(y => y.role_id != x.role_id)).tolist();               foreach (role roletodelete in rolestoremove.tolist())             {                 // remove roles rolestoremove                 user.roles.remove(roletodelete);              }              //add roles not in list of rolestoadd             foreach (role rol in rolestoadd)             {                 var newrole = new role { role_id = rol.role_id };                 context.roles.attach(newrole);                 user.roles.add(newrole);              }              context.savechanges();             return entity;         }     } 

what i'm missing?

to remove entities entity it's necessary entities loaded before in entity.

try with

var user = context.users.include(u => u.roles).where(u => u.user_id == entity.user_id).firstordefault;  list<role> rolestoremove =     user.roles.where(x => entity.roles.all(y => y.role_id != x.role_id)).tolist();  //roles add list<role> rolestoadd =     entity.roles.where(x => user.roles.all(y => y.role_id != x.role_id)).tolist();