using System;

using System.Collections;

using System.Collections.Generic;

using System.Linq;

public class Program

{

    public static void Main()

    {

        var metrics = new List<Metrics>() 

        {

            new Metrics { Id = 1, Metric = "Metric 1" },

            new Metrics { Id = 2, Metric = "Metric 2" },

            new Metrics { Id = 3, Metric = "Metric 2" }

        };

​

        var metricValuePerPerson = new List<MetricsValuePerPerson>() 

        {

            new MetricsValuePerPerson { Id = 1, PersonId = 1, MetricId = 1, Value = "Test 1" },

            new MetricsValuePerPerson { Id = 2, PersonId = 1, MetricId = 2, Value = "Test 2" },

            new MetricsValuePerPerson { Id = 3, PersonId = 1, MetricId = 3, Value = "Test 3" }

        };

​

        var result = metricValuePerPerson.GroupJoin(metrics, mv => new { Id = mv.PersonId }, m => new { Id = m.Id }, 

        (mv, m) => new { mv = mv, m = m })

        .SelectMany(x => x.m.DefaultIfEmpty(), (x, y) => new {mv = x.mv, m = y })

        .GroupBy(g => g.mv.PersonId)

        .Select(x =>  

        {

           var grouped = x.ToList();

           return new 

            {

                PersonId = x.Key,//The below are sample code, please use your actual code.

                Metric1 = grouped[0].mv.PersonId + "|" + grouped[0].m.Metric + "|" + grouped[0].mv.Value,

                Metric2 = grouped[1].mv.PersonId + "|" + grouped[1].m.Metric + "|" + grouped[1].mv.Value,

                Metric3 = grouped[2].mv.PersonId + "|" + grouped[2].m.Metric + "|" + grouped[2].mv.Value,

            };

        })

        .ToList();

​

    foreach (var item in result)

        Console.WriteLine(item);

    }

}

​

public class  Metrics

{

    public int Id { get; set; }

​

    public string Metric { get; set; }

}

​

public class MetricsValuePerPerson

{

    public int Id { get; set; }

​

    public int PersonId { get; set; }

​

    public int MetricId { get; set; }

​

    public string Value { get; set; }

}