DotNETFrameworkVersionDetect.cs

## DotNETFrameworkVersionDetect.cs
void Main()
{
    Get45or451FromRegistry();
}

private static void Get45or451FromRegistry()
{
    using (RegistryKey ndpKey = RegistryKey.OpenBaseKey(RegistryHive.LocalMachine, RegistryView.Registry32).OpenSubKey("SOFTWARE\\Microsoft\\NET Framework Setup\\NDP\\v4\\Full\\"))
    {
        if (ndpKey != null && ndpKey.GetValue("Release") != null)
        {
            Console.WriteLine("Version: " + CheckFor45DotVersion((int)ndpKey.GetValue("Release")));
        }
        else
        {
            Console.WriteLine("Version 4.5 or later is not detected.");
        }
    }
}

// Checking the version using >= will enable forward compatibility,
// however you should always compile your code on newer versions of
// the framework to ensure your app works the same.
private static string CheckFor45DotVersion(int releaseKey)
{
    if (releaseKey >= 393295)
    {
        return "4.6 or later";
    }
    if ((releaseKey >= 379893))
    {
        return "4.5.2 or later";
    }
    if ((releaseKey >= 378675))
    {
        return "4.5.1 or later";
    }
    if ((releaseKey >= 378389))
    {
        return "4.5 or later";
    }
    // This line 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";
}