C# using Linq in Queryable

Question

I'm a bit new to Linq and hoping someone could help me on something I'm currently strugling.

I currently have 2 list

public IQueryable<TRole> Roles
{
   get
   {
      var roles = new List<TRole>();
      roles.Add(CreateIdentityRole("Chairman", "Voorzitter"));
      roles.Add(CreateIdentityRole("Treasurer", "Penningmeester"));
      roles.Add(CreateIdentityRole("Ranking Responsible", "Rankingverantwoordelijke"));
                roles.Add(CreateIdentityRole("Competition Responsible", "Competitieverantwoordelijke"));
      roles.Add(CreateIdentityRole("Webmaster", "Webbeheerder"));
      roles.Add(CreateIdentityRole("Secretary", "Secretaris"));
      foreach(TRole role in roles)
      {
         if (!_roles.Contains(role))
            _roles.Add(role);
      }

      return _roles.AsQueryable<TRole>();
   }
}

private TRole CreateIdentityRole(string id, string name)
{
   TRole role = (TRole)Activator.CreateInstance(typeof(TRole));
   role.Id = id;
   role.Name = name;
   return role;
}

public void InitializePrivacy(IdentityUser user)
{
   var manager = Context.GetOwinContext().GetUserManager<ApplicationUserManager>();
   var roleManager = new RoleStore<IdentityRole>();
   var roles = roleManager.Roles;
   List<string> userRoles = manager.GetRoles(user.Id);
}

right now I want to use Linq to get all roles which are not found in userRoles. Because the roles is a Queryable I do not really now how to achieve such result.

Queryable is a static class which provides methods for IQueryable implementations. You can't create an instance of it. — Chris Pickford
– Chris Pickford, Commented Apr 6, 2017 at 10:53
the Querable is achieved in another function. This is made to have an example of what I need to achieve. I adapted my script to show you where its created. — Davy Quyo
– Davy Quyo, Commented Apr 6, 2017 at 10:57

daniell89 · Accepted Answer · 2017-04-06 11:01:04Z

2

You can use IEnumerable interface. If your method return Querable result it will work. Try this:

IEnumerable<string> roles = roleManager.Roles;
List<string> userRoles = GetRoles(user.Id);

var result = roles.Except(userRoles);

answered Apr 6, 2017 at 11:01

daniell89

2,34220 silver badges28 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Marco · Accepted Answer · 2017-04-06 11:00:58Z

2

A simple .Except() should probably be enough:

using System.Linq;
//...
var roles = roleManager.Roles.ToList();
List<string> userRoles = manager.GetRoles(user.Id);
var ununsedRoles = roles.Execpt(userRoles);

This will give you all items roles, except those in userRoles.

MSDN: https://msdn.microsoft.com/en-us/library/bb300779(v=vs.110).aspx

answered Apr 6, 2017 at 11:00

Marco

24.1k13 gold badges81 silver badges132 bronze badges

Comments

Chris Pickford · Accepted Answer · 2017-04-06 11:00:46Z

1

To get a collection of Roles that are not found in userRoles:

var rolesNotFound = roleManager.Roles
                      .Where(r => !userRoles.Select(u => u.Id).Contains(r.Id))
                      .ToList();

answered Apr 6, 2017 at 11:00

Chris Pickford

9,0606 gold badges51 silver badges76 bronze badges

1 Comment

Davy Quyo Over a year ago

I was hoping to see someone doing the same thing in a more complicated way to get more understanding. thx. I appreciate it.

Collectives™ on Stack Overflow

C# using Linq in Queryable

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

3 Answers 3

Comments

Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related