C# group list and put count into list variable

Question

I have got a list which looks like this for example:

Id = 1, Name = Microsoft, Country = USA, Match = null
Id = 2, Name = Google,    Country = USA, Match = null
Id = 1, Name = Microsoft, Country = USA, Match = null

Now I would like to group the list by name which I did like this:

var List = result.GroupBy(x => x.Name).ToList();

My goal is to safe the number of duplicates into Match. So that the list looks like this:

Id = 1, Name = Microsoft, Country = USA, Match = 2
Id = 2, Name = Google,    Country = USA, Match = 1

Thanks in advance!

Sergey Berezovskiy · Accepted Answer · 2017-05-10 15:44:17Z

7

I would group by all three properties thus they will have same values for all item in the group. That will simplify building aggregated entity:

var List = result.GroupBy(x => new { x.Name, x.Id, x.Country })
             .Select(g => new YourType { 
                 Id = g.Key.Id,
                 Name = g.Key.Name,
                 Country = g.Key.Country,
                 Match = g.Count()
             })
             .ToList();

If you have Microsoft in other countries (not only USA) and you want to get the number of duplicates for company Name only (whether it is located in USA or not), then you should remove Country both from key and from aggregated entity.

edited May 10, 2017 at 15:44

answered May 10, 2017 at 15:37

Sergey Berezovskiy

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3 Comments

Tom el Safadi Over a year ago

Thanks, that did it!

Tom el Safadi Over a year ago

If I only want to group by Name and not by Country but still want to include the country in the list how would I do that?

Sergey Berezovskiy Over a year ago

@Anokrize then you should define which Country you want to include. Because there will be several entities with same name, but different countries

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