How to get Windows Version - as in "Windows 10, version 1607"?

according to MSDN official link there's a specific version number for each windows version out there. in dot net this can be read using the Environment.OSVersion object.

Console.WriteLine("OSVersion: {0}", Environment.OSVersion);
//output: OSVersion: Microsoft Windows NT 6.2.9200.0

What you are looking for is called ReleaseID not a version of windows. this be can read from registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\ReleaseId

using Microsoft.Win32;

string releaseId = Registry.GetValue(@"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion", "ReleaseId", "").ToString();
Console.WriteLine(releaseId);

 private static ManagementObject GetMngObj(string className)
    {
        var wmi = new ManagementClass(className);

        foreach (var o in wmi.GetInstances())
        {
            var mo = (ManagementObject)o;
            if (mo != null) return mo;
        }

        return null;
    }

    public static string GetOsVer()
    {
        try
        {
            ManagementObject mo = GetMngObj("Win32_OperatingSystem");

            if (null == mo)
                return string.Empty;

            return mo["Version"] as string;
        }
        catch (Exception e)
        {
            return string.Empty;
        }
    }

How to Use:

Console.WriteLine(GetOsVer());

Result: 10.0.0.1299

In addition to Scott's answer, you can also get the product name (ex. Windows 10 Pro) with this (*I take no credit as Scott is the one who mentioned the registry path + I'm reusing his code below):

using Microsoft.Win32;

string ProductName = 
Registry.GetValue(@"HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion", "ProductName", "").ToString();
Console.WriteLine(ProductName);

string Version = (string)Registry.GetValue(@"HKEY_LOCAL_MACHINE\SOFTWARE\WOW6432Node\Microsoft\Windows NT\CurrentVersion", "ProductName", null);

Gives a name like "Windows 10 Enterprise".