get the DotNetFramework path using ToolLocationHelper

program.cs

using Microsoft.Build.Utilities;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace DotNetPaths
{
    class Program
    {
        static void Main(string[] args)
        {
            var sb = new StringBuilder();
            var methods = typeof(ToolLocationHelper).GetMethods();
            foreach (var method in methods)
            {
                if (typeof(string) == method.ReturnType &&
                    method.GetParameters().Count() == 1 &&
                    method.GetParameters()[0].ParameterType == typeof(TargetDotNetFrameworkVersion))
                {
                    var result = (string)method.Invoke(null, new object[] { TargetDotNetFrameworkVersion.VersionLatest });
                    sb.AppendLine(string.Format("[{0}]", method.Name));
                    sb.AppendLine(string.Format("  {0}", result));
                }
            }

            Console.Out.WriteLine(sb.ToString());

            var fs = new StreamWriter("output.txt");
            fs.Write(sb.ToString());
            fs.Close();
        }
    }
}