Find multiple duplicate values in a list in c#

Question

So, lets say I have a list of cars. Each item in the list has a brand and a color property. I would like to find out for each brand how many there are of the same color, and then print that info. The list will be filled by user input. There's no way for me to tell which exact values will be in the list.

Example:

class Car
    {
        public string brand;
        public string color;
    }

    private void DoSomething()
    {
        List<Car> cars = new List<Car>();
        cars.Add(new Car { brand = "Toyota", color = "blue" });
        cars.Add(new Car { brand = "Toyota", color = "red" });
        cars.Add(new Car { brand = "Toyota", color = "blue" });
        cars.Add(new Car { brand = "Audi", color = "red" });
        cars.Add(new Car { brand = "Audi", color = "red" });
        cars.Add(new Car { brand = "Audi", color = "blue" });

        // Find out for each brand how many there are of the same color, and then print that info
        // Example output: Toyota: 2 blue, 1 red
        //                 Audi:   2 red, 1 blue
    }

I've spend a long time searching for a way to do this. All I was able to figure out was how to get the number of occurences of a certain item in the list.

If my question is unclear please let me know, I will try to explain a bit more.

You could use LINQ to do this. If you aren't familiar with LINQ, it'll require a bit of research, maybe some headache at first. But you'll end up with fairly simple code. — Broots Waymb
– Broots Waymb, Commented Jul 5, 2017 at 16:00

MakePeaceGreatAgain · Accepted Answer · 2017-07-05 16:05:42Z

4

Some linq should do this:

var result = cars.GroupBy(x => new { x.brand, x.color })
    .Select(x => new { 
        Brand = x.Key.brand, 
        Color = x.Key.color, 
        Count = x.Count() 
    });

answered Jul 5, 2017 at 16:05

MakePeaceGreatAgain

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1 Comment

Joey040 Over a year ago

Thank you, this worked for me. All I had to do after this was iterate over the results with a loop. I'll definately have to learn some more about LINQ!

jAC · Accepted Answer · 2017-07-05 16:06:17Z

3

var carGroups = cars.GroupBy(c => new { c.brand, c.color });
foreach (var carGroup in carGroups)
{
    Console.WriteLine($"{carGroup.Key}, count: {carGroup.Count()}");
}

answered Jul 5, 2017 at 16:06

jAC

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2 Comments

Joey040 Over a year ago

Thank you for your answer! This could work for me, however the accepted answer gives me better results in my case.

jAC Over a year ago

You're welcome. No problem at all, you should accept the answer that suits the question most. If it's HimBromBeere's answer, then he deserves the reputation.

huMpty duMpty · Accepted Answer · 2017-07-05 16:06:26Z

1

  var grp = cars.GroupBy(g => new { g.brand, g.color }).Select(n => new {
                brand = n.Key.brand,
                color = n.Key.color,
                count = n.Count()

            });

answered Jul 5, 2017 at 16:06

huMpty duMpty

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