使用C#代码下载.nupkg 包

代码：

        public static async Task DownloadAsync(string packageId, string version)
        {
            var package = new PackageIdentity(packageId, NuGetVersion.Parse(version));

            var settings = Settings.LoadDefaultSettings(null);
            var globalFolder = SettingsUtility.GetGlobalPackagesFolder(settings);

            var logger = NullLogger.Instance;
            var cancelToken = CancellationToken.None;

            var sourceRepositoryProvider = new SourceRepositoryProvider(settings, Repository.Provider.GetCoreV3());
            var downloadFolder = Path.Combine(AppDomain.CurrentDomain.BaseDirectory, "Download");
            using (var cacheContext = new SourceCacheContext())
            {
                var downloadContext = new PackageDownloadContext(cacheContext, downloadFolder, true);

                var repositories = sourceRepositoryProvider.GetRepositories();
                foreach (var repository in repositories)
                {
                    var downloadResult = await PackageDownloader.GetDownloadResourceResultAsync(repository,
                                                                                                package,
                                                                                                downloadContext,
                                                                                                globalFolder,
                                                                                                logger,
                                                                                                cancelToken);

                    if (downloadResult != null)
                    {
                        var downloadFile = $@" {downloadFolder} \ {package.Id} . {package.Version} .nupkg";

                        using (var fileStream = File.Create(downloadFile))
                        {
                            downloadResult.PackageStream.Seek(0, SeekOrigin.Begin);
                            await downloadResult.PackageStream.CopyToAsync(fileStream);
                        }

                        break;
                    }
                }
            }
        }