using System;

using System.Collections.Generic;

using System.Linq.Expressions;

using System.Linq;

​

public class Program

{

    public static void Main()

    {

        var list = new List<Item>();

        list.Add(Create(Letter.A));

        list.Add(Create(Letter.B));

        list.Add(Create(Letter.C));

        list.Add(Create(Letter.C));

        var dict = list.Percentage(x => x.Letter1);

        dict.Dump();

    }

    private static Item Create(Letter letter)

    {

        return new Item

        {

            Letter1 = letter

        };

    }

}

​

public static class Extensions

{

    public static Dictionary<TProperty, double> Percentage<T, TProperty>(this IEnumerable<T> source, Expression<Func<T,TProperty>> selector)

    {

        var dict = new Dictionary<TProperty, double>();

        Func<T,TProperty> func = selector.Compile();

        var list = source.ToList();

        var groups = list.GroupBy(func).ToList();

        double total = list.Count;

        foreach(var group in groups)

        {

            double groupCount = group.Count();

            var percentage = (groupCount / total) * 100;

            dict.Add(group.Key, percentage);

        }

        return dict;

    }

}

​

​

public class Item

{

    public Letter Letter1 {get;set;} 

}

​

public enum Letter

{

    A,

    B,

    C

}