Save many to many relation via view model in entity framework 6 - entity-framework

Question

I have two entities (TaskStep and Role) with many to many relation, I use a view model (named StepViewModel) to display taskstep and it's allowed Roles, StepViewModel is :
public class StepViewModel
{
public StepViewModel()
{
}
public TaskStep TaskStep { get; set; }
public virtual ICollection<AllowedRole> AllowedRole { get; set; }
}
and I use this method to display taskstep:
public static StepViewModel GetTaskStepData(int stepId)
{
using (var context = new WFContext())
{
return context.TaskSteps.Where(ts => ts.ID == stepId).Include(ts => ts.Roles)
.Select(ts => new StepViewModel()
{
AllowedRole = context.Roles.Select(r => new AllowedRole()
{
Role = r,
Allowed = ts.Roles.Select(x => x.ID).Contains(r.ID)
}).ToList(),
TaskStep = ts
})
.SingleOrDefault();
}
}
but when I save the taskstep, it's roles changes don't save. My save method is :
public static void SaveTaskStep(StepViewModel stepViewModel)
{
using (var context = new WorkFlowContext())
{
//TaskStep taskStep = context.TaskSteps.Where(ts => ts.ID == stepViewModel.TaskStep.ID).Include(ts => ts.Roles).SingleOrDefault();
TaskStep taskStep = stepViewModel.TaskStep;
List<int> aRolesIDs = stepViewModel.AllowedRole.Where(ar => ar.Allowed == true).Select(ar => ar.Role.ID).ToList();
List<Role> roles = context.Roles.Where(r => aRolesIDs.Contains(r.ID)).Include(r => r.AllowedTaskSteps).ToList();
taskStep.Roles.Clear();
foreach (Role role in roles)
{
if (context.Entry(role).State == EntityState.Detached)
context.Roles.Attach(role);
taskStep.Roles.Add(role);
}
if (taskStep.ID == 0)
context.TaskSteps.Add(taskStep);
else
context.Entry(taskStep).State = EntityState.Modified;
context.SaveChanges();
}
}
if I get taskstep from db with include roles (like first -comment- line in save method), it work's well. but in this way, I have to make all taskstep field's changes manually. In addition when I assign taskstep to stepviewmodel,I use "include" but it's still doesn't work.what can I do to save stepViewModel roles?

Answer 1

context.TaskSteps.Attach(taskStep) should work in your case
SaveTaskStep method:
using (var context = new WorkFlowContext())
{
TaskStep taskStep = stepViewModel.TaskStep;
if (taskStep.ID == 0)
context.TaskSteps.Add(taskStep);
else
context.TaskSteps.Attach(taskStep); //from this point EF start change tracking
//I just copy-pasted this part your code assuming it's correct
List<int> aRolesIDs = stepViewModel.AllowedRole.Where(ar => ar.Allowed == true).Select(ar => ar.Role.ID).ToList();
List<Role> roles = context.Roles.Where(r => aRolesIDs.Contains(r.ID)).Include(r => r.AllowedTaskSteps).ToList();
taskStep.Roles.Clear();
foreach (Role role in roles)
{
if (context.Entry(role).State == EntityState.Detached)
context.Roles.Attach(role);
taskStep.Roles.Add(role);
}
context.SaveChanges();
} // end of using (var context