在列表中查找最常出现的项目的方法

Question

Ok, so I have a project about a carpark. Long story short I need a method to find most often occurring model in a data list. Any good ways to approach this (Using VST 2012)

private static int FilterbyModel(string Model, List<Car> cars)


  {
        int modelCount = 0;
        List<string> Modelis = new List<string>();
        foreach (Car s in cars)
        {
            if (s.Modelis == Model)
            {
                if (!Model.Contains(s.Modelis)) 
                {
                    Modelis.Add(s.Modelis);
                    modelCount++;
                }
            }
            return modelCount;

Above method would work, but I need to provide a specific model to look for rather than to just find the most common one.

Answer 1

Simplest way to count occurrences is to group by model and then count each group's elements. Here I give an example with LINQ:

var carsByModel = cars.GroupBy(x => x.Model)
    .Select(x => new { Model = x.Key, Count = c.Count() });

Now if you want to order them and pick the most common one:

var mostCommonCar = carsByModel.OrderByDescending(x => x.Count).First();

If, for example, you need to print the two most common models:

foreach (var model in carsByModel.OrderByDescending(x => x.Count).Take(2))
    Console.WriteLine($"{model.Model}: {model.Count}");

Or the less common twos:

foreach (var model in carsByModel.OrderBy(x => x.Count).Take(2))
    Console.WriteLine($"{model.Model}: {model.Count}");

---

If in that count you're interested in one specific model you may do this (note that I do omit StringComparer in this example but I always suggest to use it in production code):

carsByModel.First(x => x.Model.Equals("modelYouWant"));

However note that if you just need to count occurrences of a specific model then this is faster and simpler:

int occurencesOfModelIWant = cars.Count(x => x.Model.Equals("modelYouWant"));