.NET Framework 2.0で動くC# 7.0コード

Program.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Runtime.CompilerServices;

namespace ConsoleAppFx2_0
{
    class Program
    {
        static void Main(string[] args)
        {
            var inputs = new[] { A(), B(), C(), D() };
            var outputs =
                from x in inputs
                where x.line % 2 == 1
                select $"line: {x.line}, name: {x.name}";

            foreach (var x in outputs)
            {
                Console.WriteLine(x);
            }
        }

        static (int line, string name) CallerInfo(
            [CallerLineNumber] int line = 0,
            [CallerMemberName] string name = null)
            => (line, name);

        static (int line, string name) A() => CallerInfo();
        static (int line, string name) B() => CallerInfo();
        static (int line, string name) C() => CallerInfo();
        static (int line, string name) D() => CallerInfo();
    }
}

namespace System
{
    public delegate void Action();
    public delegate TResult Func<T1, TResult>(T1 x1);

    public struct ValueTuple
    {
        public static ValueTuple<T1, T2> Create<T1, T2>(T1 item1, T2 item2) => new ValueTuple<T1, T2>(item1, item2);
    }

    public struct ValueTuple<T1, T2>
    {
        public T1 Item1;
        public T2 Item2;
        public ValueTuple(T1 item1, T2 item2) { Item1 = item1; Item2 = item2; }
    }
}

namespace System.Linq
{
    public static class Enumerable
    {
        public static IEnumerable<U> Select<T, U>(this IEnumerable<T> source, Func<T, U> filter)
        {
            if (source == null) throw new ArgumentNullException(nameof(source));
            if (filter == null) throw new ArgumentNullException(nameof(filter));
            IEnumerable<U> f()
            {
                foreach (var x in source) yield return filter(x);
            }
            return f();
        }

        public static IEnumerable<T> Where<T>(this IEnumerable<T> source, Func<T, bool> predicate)
        {
            if (source == null) throw new ArgumentNullException(nameof(source));
            if (predicate == null) throw new ArgumentNullException(nameof(predicate));
            IEnumerable<T> f()
            {
                foreach (var x in source) if (predicate(x)) yield return x;
            }
            return f();
        }
    }
}

namespace System.Runtime.CompilerServices
{
    public sealed class ExtensionAttribute : Attribute { }
    public sealed class CallerLineNumberAttribute : Attribute { }
    public sealed class CallerMemberNameAttribute : Attribute { }
    public sealed class TupleElementNamesAttribute : Attribute
    {
        public TupleElementNamesAttribute(string[] transformNames) => TransformNames = transformNames;
        public IList<string> TransformNames { get; }
    }
}