Microsoft.Win32 System System.Collections.ObjectModel class Program { static void Main(string[] args) { InstalledDotNetVersions().Dump(); } public static Collection InstalledDotNetVersions() { Collection versions = new Collection(); RegistryKey NDPKey = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\NET Framework Setup\NDP"); if (NDPKey != null) { string[] subkeys = NDPKey.GetSubKeyNames(); foreach (string subkey in subkeys) { GetDotNetVersion(NDPKey.OpenSubKey(subkey), subkey, versions); GetDotNetVersion(NDPKey.OpenSubKey(subkey).OpenSubKey("Client"), subkey, versions); GetDotNetVersion(NDPKey.OpenSubKey(subkey).OpenSubKey("Full"), subkey, versions); } } return versions; } private static void GetDotNetVersion(RegistryKey parentKey, string subVersionName, Collection versions) { if (parentKey != null) { string installed = Convert.ToString(parentKey.GetValue("Install")); if (installed == "1") { string version = Convert.ToString(parentKey.GetValue("Version")); if (string.IsNullOrEmpty(version)) { if (subVersionName.StartsWith("v")) version = subVersionName.Substring(1); else version = subVersionName; } Version ver = new Version(version); if (!versions.Contains(ver)) versions.Add(ver); } } } }