Retrieve the current CRM version

The CRM SDK DLLs can easily connect to different CRM versions, for example the CRM 2013 DLLs can be used also with CRM 2011/2015 environments.
Depending the version some messages (like the ExecuteMultipleRequest) are not available, the following function returns an enumerator with the current CRM version.

public enum CRMVersion
{
    Unknown,
    CRM2011,
    CRM2011UR12PLUS,
    CRM2013,
    CRM2013SP1,
    CRM2015
}

public CRMVersion GetCRMVersion(IOrganizationService service)
{
    RetrieveVersionRequest versionRequest = new RetrieveVersionRequest();
    RetrieveVersionResponse versionResponse = (RetrieveVersionResponse)service.Execute(versionRequest);

    string version = versionResponse.Version;
    if (version.StartsWith("5"))
    {
        try
        {
            int buildNumber = Convert.ToInt32(version.Substring(version.LastIndexOf(".") + 1));
            if (buildNumber > 3000) { return CRMVersion.CRM2011UR12PLUS; }
        }
        catch { }
        return CRMVersion.CRM2011;
    }
    if (version.StartsWith("6.0")) { return CRMVersion.CRM2013; }
    if (version.StartsWith("6.1")) { return CRMVersion.CRM2013SP1; }
    if (version.StartsWith("7")) { return CRMVersion.CRM2015; }
    return CRMVersion.Unknown;
}