GetDotNetVersion.cs

using Microsoft.Win32;
using System;

namespace BotwTrainer
{
    public class GetDotNetVersion
    {
        public NetVersion Get45PlusFromRegistry()
        {
            var netVersion = new NetVersion();

            const string subkey = @"SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full\";
            using (RegistryKey ndpKey = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry32).OpenSubKey(subkey))
            {
                if (ndpKey != null && ndpKey.GetValue("Release") != null)
                {
                    netVersion.Details = ".NET Framework Version: " + CheckFor45PlusVersion((int)ndpKey.GetValue("Release"));
                    netVersion.Version = CheckFor45PlusVersion((int)ndpKey.GetValue("Release"));
                    netVersion.ReleaseKey = (int)ndpKey.GetValue("Release");
                }
                else
                {
                    netVersion.Details = ".NET Framework Version 4.5 or later is not detected.";
                    netVersion.Version = null;
                    netVersion.ReleaseKey = 0;
                }
            }

            return netVersion;
        }

        // Checking the version using >= will enable forward compatibility.
        private static string CheckFor45PlusVersion(int releaseKey)
        {
            if (releaseKey >= 460798)
            {
                return "4.7 or later";
            }
            if (releaseKey >= 394802)
            {
                return "4.6.2";
            }
            if (releaseKey >= 394254)
            {
                return "4.6.1";
            }
            if (releaseKey >= 393295)
            {
                return "4.6";
            }
            if ((releaseKey >= 379893))
            {
                return "4.5.2";
            }
            if ((releaseKey >= 378675))
            {
                return "4.5.1";
            }
            if ((releaseKey >= 378389))
            {
                return "4.5";
            }
            // This code should never execute. A non-null release key should mean
            // that 4.5 or later is installed.
            return "No 4.5 or later version detected";
        }
    }

    public class NetVersion
    {
        public string Version { get; set; }

        public string Details { get; set; }

        public int ReleaseKey { get; set; }
    }
}