How can I use Linq to get distinct results filtered by property

Question

Given this class:

public class Tool
    {
        public int Id { get; set; }
        public int Number { get; set; }
        public string Source { get; set; }
    }

And a list of Tools like this:

var tools = new List<Tool>()
            {
                new Tool {Id=444, Number=121, Source="Master"},
                new Tool {Id=777, Number=121, Source="M1"},
                new Tool {Id=333, Number=51, Source="Master"},
                new Tool {Id=555, Number=61, Source="Master"},
                new Tool {Id=848, Number=51, Source="M1"}
                //Many more
            };

How could I use Linq to get a list of distinct Tools by Number and if 2 tools have the same Number select the one whose source is "M1", i.e.the resulting list would contain:

Tool {Id=777, Number=121, Source="M1"}
Tool {Id=848, Number=51, Source="M1"}
Tool {Id=555, Number=61, Source="Master"}

Sajeetharan · Answer 1 · 2018-01-10T19:34:36.597

2

Try grouping by Number and get the first element of that,

List<Tool> distinctTool = tools.GroupBy(p => p.Number)
                               .Select(f => f.OrderByDescending(q => q.Source == "M1").First())
                               .ToList();

WORKING FIDDLE

edited Jan 10 '18 at 19:34

answered Jan 10 '18 at 19:13

Sajeetharan

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This does not deal with prioritizing the `M1` source – JamesFaix Jan 10 '18 at 19:21
ok ok guys! it happens:) – Sajeetharan Jan 10 '18 at 19:23
@JamesFaix Corrrected – Sajeetharan Jan 10 '18 at 19:27
You still need to update your query to Group By with `Number`, not with `Source` . its giving the wrong results. – Ehsan Ullah Nazir Jan 10 '18 at 19:33
@EhsanUllahNazir Thanks for that correction, that was my initial answer – Sajeetharan Jan 10 '18 at 19:35
Welcome , It happens :) – Ehsan Ullah Nazir Jan 10 '18 at 19:36

score 2 · Answer 2 · answered Jan 10 '18 at 19:17

2

You need to group your Tools by Number and get the First() of them

List<Tool> distinctTool = tools
  .GroupBy(p => p.Number)
  .Select(g => g.OrderByDescending(q => q.Source == "M1").First())      
  .ToList();

answered Jan 10 '18 at 19:17

Ehsan Ullah Nazir

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score 2 · Accepted Answer · answered Jan 10 '18 at 19:18

2

List<Tool> distinctTool = tools
  .GroupBy(p => p.Number)
  .Select(g => g.OrderByDescending(q => q.Source == "M1").First())
  .ToList();

answered Jan 10 '18 at 19:18

koryakinp

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How can I use Linq to get distinct results filtered by property

3 Answers3