using System;

using System.Linq.Expressions;

using System.Threading.Tasks;

using System.Linq;

using System.Reflection;

using System.Collections.Generic;

​

​

public class Program

{

    public static void Main()

    {

            var vs = Enumerable.Range(0, 50).Select(i => Create(i));

            var groups = vs.GroupByKeys(new [] { "Scale" });

            Console.WriteLine("{0} groups", groups.Count());

            Console.WriteLine(string.Join(", ", groups.Select(g => g.Key)));

​

    }

    static Employee Create(int i) {

        return new Employee { Scale = (((int)(i / 10)) * 10), DOB = new DateTime(2011, 11, 11), Sales = 50000 };

    }

​

​

}

​

    public class Employee

    {

        public string Designation {get ;set;}

        public string Discipline {get ;set;}

        public int Scale {get ;set;}

        public DateTime DOB {get ;set;}

        public int Sales {get ;set;}

    }

    public static class GroupByExtensions 

    {

        public static IEnumerable<IGrouping<string, TValue>> GroupByKeys<TValue>(this IEnumerable<TValue> values, IEnumerable<string> keys) 

        {

            var getters = typeof(TValue).GetProperties(BindingFlags.Instance | BindingFlags.Public | BindingFlags.GetProperty)

                .Where(pi => keys.Contains(pi.Name))

                .Select(pi => pi.GetMethod)

                .Where(mi => mi != null)

                .ToArray();

            if (keys.Count() != getters.Length) 

            {

                throw new InvalidOperationException("Couldn't find all keys for grouping");

            }

            return values.GroupBy(v => getters.Aggregate("", (acc, getter) => string.Format("{0}¬{1}", acc, getter.Invoke(v, null).ToString())));

        }

    }