NuGet.PackageReferenceFile.GetPackageReferences C# (CSharp) Method

        public IEnumerable<PackageReference> GetPackageReferences()
        {
            XDocument document = GetDocument();

            if (document == null)
            {
                yield break;
            }

            foreach (var e in document.Root.Elements("package"))
            {
                string id = e.GetOptionalAttributeValue("id");
                string versionString = e.GetOptionalAttributeValue("version");
                string versionConstraintString = e.GetOptionalAttributeValue("allowedVersions");
                string targetFrameworkString = e.GetOptionalAttributeValue("targetFramework");
                SemanticVersion version;

                if (String.IsNullOrEmpty(id) || String.IsNullOrEmpty(versionString))
                {
                    // If the id or version is empty, ignore the record.
                    continue;
                }

                if (!SemanticVersion.TryParse(versionString, out version))
                {
                    throw new InvalidDataException(String.Format(CultureInfo.CurrentCulture, NuGetResources.ReferenceFile_InvalidVersion, versionString, _path));
                }

                IVersionSpec versionConstaint = null;
                if (!String.IsNullOrEmpty(versionConstraintString))
                {
                    if (!VersionUtility.TryParseVersionSpec(versionConstraintString, out versionConstaint))
                    {
                        throw new InvalidDataException(String.Format(CultureInfo.CurrentCulture, NuGetResources.ReferenceFile_InvalidVersion, versionConstraintString, _path));
                    }

                    _constraints[id] = versionConstraintString;
                }

                FrameworkName targetFramework = null;
                if (!String.IsNullOrEmpty(targetFrameworkString))
                {
                    targetFramework = VersionUtility.ParseFrameworkName(targetFrameworkString);
                    if (targetFramework == VersionUtility.UnsupportedFrameworkName)
                    {
                        targetFramework = null;
                    }
                } 

                yield return new PackageReference(id, version, versionConstaint, targetFramework);
            }
        }

        public static ICollection <PackageReference> GetPackageReferences(PackageReferenceFile file, string fileName, bool requireVersion)
        {
            if (file == null)
            {
                throw new ArgumentNullException("file");
            }

            var packageReferences = file.GetPackageReferences(requireVersion).ToList();

            foreach (var package in packageReferences)
            {
                // GetPackageReferences returns all records without validating values. We'll throw if we encounter packages
                // with malformed ids / Versions.
                if (String.IsNullOrEmpty(package.Id))
                {
                    throw new InvalidDataException(String.Format(CultureInfo.CurrentCulture, NuGetResources.InstallCommandInvalidPackageReference, fileName));
                }
                if (requireVersion && (package.Version == null))
                {
                    throw new InvalidDataException(String.Format(CultureInfo.CurrentCulture, NuGetResources.InstallCommandPackageReferenceInvalidVersion, package.Id));
                }
            }

            return(packageReferences);
        }