private static ValidationResult ValidateVersion(NuGetVersion version)
        {
            if (version.IsSemVer200())
            {
                return new ValidationResult(string.Format(
                    CultureInfo.CurrentCulture,
                    Strings.Manifest_InvalidVersionSemVer200,
                    version.ToFullString()));
            }
            else if (!version.IsValidVersionForLegacyClients())
            {
                return new ValidationResult(string.Format(
                    CultureInfo.CurrentCulture,
                    Strings.Manifest_InvalidVersion,
                    version));
            }

            return null;
        }