Use linq distinct function?

Question

How can I use linq distinct operator here to remove remove duplicate courses.Cours.Name,

var coursesList = from courses in not_subsribe
  select new SelectListItem
  {
      Text = courses.Cours.Name,
      Value = courses.Cours.ID
      .ToString()
  };

Khurram Hassan · Answer 1 · 2014-03-11T06:28:27.323

0

You can use:

var coursesList = courses.DistinctBy(c => courses.Cours.Name)
                         .Select(crs => new SelectListItem
                                          {
                                              Text = crs.Cours.Name,
                                              Value = crs.Cours.ID.ToString()
                                          });

Sorry, I forgot to mention that DistinctBy method is available in a 3rd party library called MoreLINQ. This library is available for download using Nuget Package manager from here: http://www.nuget.org/packages/morelinq/

And you can find out more about MoreLINQ from here: https://code.google.com/p/morelinq/

edited Mar 11 '14 at 06:28

answered Mar 10 '14 at 07:36

Khurram Hassan

1,494
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1

You should at least have mentioned that `DistinctBy` is not part of .NET but of MoreLINQ. – Tim Schmelter Mar 10 '14 at 07:53
@TimSchmelter Sorry, I forgot to mention about MoreLINQ. Thanks for reminding me. – Khurram Hassan Mar 11 '14 at 06:30

Tim Schmelter · Accepted Answer · 2014-03-10T08:15:59.433

0

You could use GroupBy on an anonymous type with both properties to make them distinct:

var coursesList = 
     from c in not_subsribe
     group c by new { Id = c.Cours.ID, Name = c.Cours.Name } into g
     order by g.Key.Name
     select new SelectListItem
     {
         Text = g.Key.Name,
         Value = g.Key.Id
     };

That works because an anonymous type automatically overrides Equals+GetHashCode for you what is needed for GroupBy or Distinct. So now you could also use Distinct:

var coursesList = not_subsribe
.Select(c => new { Id = c.Cours.ID, Name = c.Cours.Name })
.Distinct()
.OrderBy(x => x.Name)
.Select(x => new SelectListItem
     {
         Text = g.Key.Name,
         Value = g.Key.Id
     });

edited Mar 10 '14 at 08:15

answered Mar 10 '14 at 07:58

Tim Schmelter

450,073
74
686
939

Or you could just `Select` the anonymous object and then call `Distinct`. – Rawling Mar 10 '14 at 08:07
@Rawling: good point, i've edited my answer. I've used `GroupBy` since OP used already query syntax and i don't like mixing query and method syntax. – Tim Schmelter Mar 10 '14 at 08:17

Use linq distinct function?

2 Answers2