using System;

using System.Collections.Generic;

using System.Linq;

using Microsoft.EntityFrameworkCore;

​

public class Program

{

    public static void Main()

    {

        using (var context = new EntityContext())

        {

            context.Database.EnsureCreated();

            var userA = new User {Location = "abc"};

            var userB = new User {Location = "abc"};

            var userC = new User {Location = "abc"};

            var userD = new User {Location = "abc"};

            var userE = new User {Location = "abc"};

            context.UserInterests.Add(new UserInterest {InterestID = 1, User = userA});

            context.UserInterests.Add(new UserInterest {InterestID = 2, User = userA});

            context.UserInterests.Add(new UserInterest {InterestID = 3, User = userA});

            context.UserInterests.Add(new UserInterest {InterestID = 1, User = userB});

            context.UserInterests.Add(new UserInterest {InterestID = 3, User = userB});

            context.UserInterests.Add(new UserInterest {InterestID = 1, User = userC});

            context.UserInterests.Add(new UserInterest {InterestID = 4, User = userC});

            context.UserInterests.Add(new UserInterest {InterestID = 1, User = userD});

            context.UserInterests.Add(new UserInterest {InterestID = 3, User = userD});

            context.UserInterests.Add(new UserInterest {InterestID = 1, User = userE});

            context.UserInterests.Add(new UserInterest {InterestID = 4, User = userE});

            context.SaveChanges();  

        }

​

        using (var context = new EntityContext())

        {

            var currentPersonId = 1;

            var data = context.UserInterests

              .Join(context.UserInterests, x => x.InterestID, x => x.InterestID, (a, b) => new { CurrentInterest = a, MatchedInterest = b })

              .Where(x => x.CurrentInterest.UserID == currentPersonId && x.MatchedInterest.UserID != currentPersonId)

              .Select(x => x.MatchedInterest.User)

              .Distinct()

              .Where(x => x.Location.StartsWith("a"))

              .OrderBy(u => Guid.NewGuid())

              .Take(2)

              .ToArray();

            FiddleHelper.WriteTable("Matched Users to UserID 1", data); 

            var list = context.UserInterests.Include(x=>x.User).ToList();

            FiddleHelper.WriteTable("All UserInterests", list); 

        }

    }

​

    public class EntityContext : DbContext

    {       

    protected override void OnConfiguring(DbContextOptionsBuilder options)

        => options.UseSqlServer(FiddleHelper.GetConnectionStringSqlServer());

        public DbSet<User> Users { get; set; }

        public DbSet<UserInterest> UserInterests { get; set; }

    }

    public class User

    {

        public int UserID { get; set; }

        public string Location { get; set; }

        public List<UserInterest> Interests { get; set; }

    }

    public class UserInterest

    {

        public int UserInterestID { get; set; }

        public int InterestID { get; set; }

        public int UserID { get; set; }

        public User User { get; set; }

    }

}