How to Check Dot Net Version Installed on the PC

This code checks the dot net version installed on the PC.

using System;
using System.Collections.Generic;
using System.Text;
using Microsoft.Win32;
using System.Windows.Forms;
namespace BusinessLayer
{
    class CheckVersion
    {
        public void Version(ListBox lbInstVersions)
        {
            string componentsKeyName = "SOFTWARE\\Microsoft\\Active Setup\\Installed Components",friendlyName,version;
            // Find out in the registry anything under: 
            // HKLM\SOFTWARE\Microsoft\Active Setup\Installed Components 
            // that has ".NET Framework" in the name 
            RegistryKey componentsKey = Registry.LocalMachine.OpenSubKey(componentsKeyName);
            string[] instComps = componentsKey.GetSubKeyNames();
            foreach (string instComp in instComps)
            {
                RegistryKey key = componentsKey.OpenSubKey(instComp);
                friendlyName = (string)key.GetValue(null); // Gets the (Default) value from this key 
                if (friendlyName != null && friendlyName.IndexOf(".NET Framework") >= 0)
                {
                    // Let's try to get any version information that's available 
                    version = (string)key.GetValue("Version");
                    // If you want only the framework info with its SP level and not the 
                    // other hotfix and service pack detail, uncomment this if: 
                    //if (version != null && version.Split(',').Length >= 4)
                    //{
                    //    if(version[0].ToString()=="2")
                        lbInstVersions.Items.Add(friendlyName + (version != null ? (" (" + version + ")") : ""));
                    //}
                }
            } 

        }
    }
}