Net Framework Installs

Program.cs

using Microsoft.Win32;
using System;
using System.Collections.Generic;

namespace ConsoleApp55
{
    class Program
    {
        static void Main(string[] args)
        {
            foreach (var version in NetFrameworkInstall.GetInstalledFrameworks())
            {
                Console.WriteLine(version);
            }
        }

        struct NetFrameworkInstall
        {
            public string Name { get; }
            public Version Version { get; }
            public string ServicePack { get; }

            NetFrameworkInstall(string name, Version version)
            {
                Name = name;
                Version = version;
                ServicePack = "";
            }

            NetFrameworkInstall(string name, Version version, string servicePack)
            {
                Name = name;
                Version = version;
                ServicePack = servicePack;
            }

            public override string ToString() =>
                $"{Name} {Version} {ServicePack}";

            public static IEnumerable<NetFrameworkInstall> GetInstalledFrameworks()
            {
                return UseNetFrameworkKey(key => new List<NetFrameworkInstall>(GetNetFxVersions(key)));

                IEnumerable<NetFrameworkInstall> GetNetFxVersions(RegistryKey ndpKey)
                {
                    foreach (string versionKeyName in ndpKey.GetSubKeyNames())
                    {
                        if (versionKeyName.Length < 1 || versionKeyName[0] != 'v')
                        {
                            continue;
                        }

                        var versionKey = ndpKey.OpenSubKey(versionKeyName);
                        var name = (string)versionKey.GetValue("Version", "");
                        var sp = versionKey.GetValue("SP", "").ToString();
                        var install = versionKey.GetValue("Install", "").ToString();

                        if (install != "" && sp != "" && install == "1")
                        {
                            yield return new NetFrameworkInstall(versionKeyName, new Version(name), sp);
                        }

                        if (name != "")
                        {
                            continue;
                        }

                        foreach (string subKeyName in versionKey.GetSubKeyNames())
                        {
                            RegistryKey subKey = versionKey.OpenSubKey(subKeyName);
                            name = (string)subKey.GetValue("Version", "");
                            if (name != "")
                                sp = subKey.GetValue("SP", "").ToString();
                            install = subKey.GetValue("Install", "").ToString();
                            if (install == "") //no install info, must be later.
                                yield return new NetFrameworkInstall(versionKeyName, new Version(name));
                            else
                            {
                                if (sp != "" && install == "1")
                                {
                                    yield return new NetFrameworkInstall(versionKeyName, new Version(name), sp);
                                }
                                else if (install == "1")
                                {
                                    yield return new NetFrameworkInstall(versionKeyName, new Version(name));
                                }
                            }
                        }
                    }
                }

                TResult UseNetFrameworkKey<TResult>(Func<RegistryKey, TResult> fn)
                {
                    using (var key = OpenNetFrameworkKey())
                    {
                        return fn(key);
                    }
                }

                RegistryKey OpenNetFrameworkKey() =>
                    RegistryKey.OpenRemoteBaseKey(RegistryHive.LocalMachine, "")
                        .OpenSubKey(@"SOFTWARE\Microsoft\NET Framework Setup\NDP\");
            }

            delegate TResult Func<in T, out TResult>(T arg);
        }
    }
}