using System;

using Microsoft.Win32;

​

// https://docs.microsoft.com/zh-tw/dotnet/framework/migration-guide/how-to-determine-which-versions-are-installed

public class Program

{

    public static void Main()

    {

        GetVersionFromRegistry();

    }

    private static void GetVersionFromRegistry()

    {

     // Opens the registry key for the .NET Framework entry.

        using (RegistryKey ndpKey = 

            RegistryKey.OpenRemoteBaseKey(RegistryHive.LocalMachine, "").

            OpenSubKey(@"SOFTWARE\Microsoft\NET Framework Setup\NDP\"))

        {

            // As an alternative, if you know the computers you will query are running .NET Framework 4.5 

            // or later, you can use:

            // using (RegistryKey ndpKey = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, 

            // RegistryView.Registry32).OpenSubKey(@"SOFTWARE\Microsoft\NET Framework Setup\NDP\"))

        foreach (string versionKeyName in ndpKey.GetSubKeyNames())

        {

            if (versionKeyName.StartsWith("v"))

            {

​

                RegistryKey versionKey = ndpKey.OpenSubKey(versionKeyName);

                string name = (string)versionKey.GetValue("Version", "");

                string sp = versionKey.GetValue("SP", "").ToString();

                string install = versionKey.GetValue("Install", "").ToString();

                if (install == "") //no install info, must be later.

                    Console.WriteLine(versionKeyName + "  " + name);

                else

                {

                    if (sp != "" && install == "1")

                    {

                        Console.WriteLine(versionKeyName + "  " + name + "  SP" + 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.

                        Console.WriteLine(versionKeyName + "  " + name);

                    else

                    {

                        if (sp != "" && install == "1")

                        {

                            Console.WriteLine("  " + subKeyName + "  " + name + "  SP" + sp);

                        }

                        else if (install == "1")

                        {

                            Console.WriteLine("  " + subKeyName + "  " + name);

                        }

                    }

                }

            }

        }

     }

   }

}