NuGet.VersionUtility.ParseOptionalVersion C# (CSharp) Method

        public static Version ParseOptionalVersion(string version)
        {
            Version versionValue;
            if (!String.IsNullOrEmpty(version) && Version.TryParse(version, out versionValue))
            {
                return versionValue;
            }
            return null;
        }

 private static XElement FindEntry(XDocument document, string id, Version version)
 {
     return((from e in document.Root.Elements("package")
             let entryId = e.GetOptionalAttributeValue("id")
                           let entryVersion = VersionUtility.ParseOptionalVersion(e.GetOptionalAttributeValue("version"))
                                              where entryId != null && entryVersion != null
                                              where id.Equals(entryId, StringComparison.OrdinalIgnoreCase) &&
                                              version.Equals(entryVersion)
                                              select e).FirstOrDefault());
 }