NOP源码分析 十一

上节讲到Head.cshtml,里面实际做的是根据supportRtl、supportResponsive、themeName三个变量,引入相应的CSS文件等。

接着看这一句:

@Html.Widget("head_html_tag")

扩展方法:

public static MvcHtmlString Widget(this HtmlHelper helper, string widgetZone, object additionalData = null)
        {
            return helper.Action("WidgetsByZone", "Widget", new { widgetZone = widgetZone, additionalData = additionalData });
        }

其实她就是调用一个action,后面是路由信息。看一下这个action:

[ChildActionOnly]
        public ActionResult WidgetsByZone(string widgetZone, object additionalData = null)
        {
            var cacheKey = string.Format(ModelCacheEventConsumer.WIDGET_MODEL_KEY, _storeContext.CurrentStore.Id, widgetZone);
            var cacheModel = _cacheManager.Get(cacheKey, () =>
            {
                //model
                var model = new List<RenderWidgetModel>();

                var widgets = _widgetService.LoadActiveWidgetsByWidgetZone(widgetZone, _storeContext.CurrentStore.Id);
                foreach (var widget in widgets)
                {
                    var widgetModel = new RenderWidgetModel();

                    string actionName;
                    string controllerName;
                    RouteValueDictionary routeValues;
                    widget.GetDisplayWidgetRoute(widgetZone, out actionName, out controllerName, out routeValues);
                    widgetModel.ActionName = actionName;
                    widgetModel.ControllerName = controllerName;
                    widgetModel.RouteValues = routeValues;

                    model.Add(widgetModel);
                }
                return model;
            });

            //no data?
            if (cacheModel.Count == 0)
                return Content("");

            //"RouteValues" property of widget models depends on "additionalData".
            //We need to clone the cached model before modifications (the updated one should not be cached)
            var clonedModel = new List<RenderWidgetModel>();
            foreach (var widgetModel in cacheModel)
            {
                var clonedWidgetModel = new RenderWidgetModel();
                clonedWidgetModel.ActionName = widgetModel.ActionName;
                clonedWidgetModel.ControllerName = widgetModel.ControllerName;
                if (widgetModel.RouteValues != null)
                    clonedWidgetModel.RouteValues = new RouteValueDictionary(widgetModel.RouteValues);

                if (additionalData != null)
                {
                    if (clonedWidgetModel.RouteValues == null)
                        clonedWidgetModel.RouteValues = new RouteValueDictionary();
                    clonedWidgetModel.RouteValues.Add("additionalData", additionalData);
                }

                clonedModel.Add(clonedWidgetModel);
            }

            return PartialView(clonedModel);
        }

看LoadActiveWidgetsByWidgetZone方法。

跟踪发现,最终通过如下方法,加载所有插件:

/// <summary>
        /// Load all widgets
        /// </summary>
        /// <param name="storeId">Load records allowed only in a specified store; pass 0 to load all records</param>
        /// <returns>Widgets</returns>
        public virtual IList<IWidgetPlugin> LoadAllWidgets(int storeId = 0)
        {
            return _pluginFinder.GetPlugins<IWidgetPlugin>(storeId: storeId).ToList();
        }

调用的是:

/// <summary>
        /// Gets plugins
        /// </summary>
        /// <typeparam name="T">The type of plugins to get.</typeparam>
        /// <param name="loadMode">Load plugins mode</param>
        /// <param name="storeId">Load records allowed only in a specified store; pass 0 to load all records</param>
        /// <param name="group">Filter by plugin group; pass null to load all records</param>
        /// <returns>Plugins</returns>
        public virtual IEnumerable<T> GetPlugins<T>(LoadPluginsMode loadMode = LoadPluginsMode.InstalledOnly, 
            int storeId = 0, string group = null) where T : class, IPlugin
        {
            return GetPluginDescriptors<T>(loadMode, storeId, group).Select(p => p.Instance<T>());
        }

调用:

/// <summary>
        /// Get plugin descriptors
        /// </summary>
        /// <typeparam name="T">The type of plugin to get.</typeparam>
        /// <param name="loadMode">Load plugins mode</param>
        /// <param name="storeId">Load records allowed only in a specified store; pass 0 to load all records</param>
        /// <param name="group">Filter by plugin group; pass null to load all records</param>
        /// <returns>Plugin descriptors</returns>
        public virtual IEnumerable<PluginDescriptor> GetPluginDescriptors<T>(LoadPluginsMode loadMode = LoadPluginsMode.InstalledOnly,
            int storeId = 0, string group = null) 
            where T : class, IPlugin
        {
            return GetPluginDescriptors(loadMode, storeId, group)
                .Where(p => typeof(T).IsAssignableFrom(p.PluginType));
        }

我们看到它取出的是IEnumerable<PluginDescriptor>  然后筛选是IWidgetPlugin的子类吧 应该是。。。

public virtual IEnumerable<PluginDescriptor> GetPluginDescriptors(LoadPluginsMode loadMode = LoadPluginsMode.InstalledOnly,
            int storeId = 0, string group = null)
        {
            //ensure plugins are loaded
            EnsurePluginsAreLoaded();

            return _plugins.Where(p => CheckLoadMode(p, loadMode) && AuthenticateStore(p, storeId) && CheckGroup(p, group));
        }

先确保插件已加载,如下:

protected virtual void EnsurePluginsAreLoaded()
        {
            if (!_arePluginsLoaded)
            {
                var foundPlugins = PluginManager.ReferencedPlugins.ToList();
                foundPlugins.Sort();
                _plugins = foundPlugins.ToList();

                _arePluginsLoaded = true;
            }
        }

看一下PluginManager:

//Contributor: Umbraco (http://www.umbraco.com). Thanks a lot! 
//SEE THIS POST for full details of what this does - http://shazwazza.com/post/Developing-a-plugin-framework-in-ASPNET-with-medium-trust.aspx

[assembly: PreApplicationStartMethod(typeof(PluginManager), "Initialize")]
namespace Nop.Core.Plugins
{
    /// <summary>
    /// Sets the application up for the plugin referencing
    /// </summary>
    public class PluginManager
    {
        #region Const

        private const string InstalledPluginsFilePath = "~/App_Data/InstalledPlugins.txt";
        private const string PluginsPath = "~/Plugins";
        private const string ShadowCopyPath = "~/Plugins/bin";

        #endregion

        #region Fields

        private static readonly ReaderWriterLockSlim Locker = new ReaderWriterLockSlim();
        private static DirectoryInfo _shadowCopyFolder;
        private static bool _clearShadowDirectoryOnStartup;

        #endregion

        #region Methods

        /// <summary>
        /// Returns a collection of all referenced plugin assemblies that have been shadow copied
        /// </summary>
        public static IEnumerable<PluginDescriptor> ReferencedPlugins { get; set; }

        /// <summary>
        /// Returns a collection of all plugin which are not compatible with the current version
        /// </summary>
        public static IEnumerable<string> IncompatiblePlugins { get; set; }

        /// <summary>
        /// Initialize
        /// </summary>
        public static void Initialize()
        {
            using (new WriteLockDisposable(Locker))
            {
                // TODO: Add verbose exception handling / raising here since this is happening on app startup and could
                // prevent app from starting altogether
                var pluginFolder = new DirectoryInfo(HostingEnvironment.MapPath(PluginsPath));
                _shadowCopyFolder = new DirectoryInfo(HostingEnvironment.MapPath(ShadowCopyPath));

                var referencedPlugins = new List<PluginDescriptor>();
                var incompatiblePlugins = new List<string>();

                _clearShadowDirectoryOnStartup = !String.IsNullOrEmpty(ConfigurationManager.AppSettings["ClearPluginsShadowDirectoryOnStartup"]) &&
                   Convert.ToBoolean(ConfigurationManager.AppSettings["ClearPluginsShadowDirectoryOnStartup"]);

                try
                {
                    var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath());

                    Debug.WriteLine("Creating shadow copy folder and querying for dlls");
                    //ensure folders are created
                    Directory.CreateDirectory(pluginFolder.FullName);
                    Directory.CreateDirectory(_shadowCopyFolder.FullName);

                    //get list of all files in bin
                    var binFiles = _shadowCopyFolder.GetFiles("*", SearchOption.AllDirectories);
                    if (_clearShadowDirectoryOnStartup)
                    {
                        //clear out shadow copied plugins
                        foreach (var f in binFiles)
                        {
                            Debug.WriteLine("Deleting " + f.Name);
                            try
                            {
                                File.Delete(f.FullName);
                            }
                            catch (Exception exc)
                            {
                                Debug.WriteLine("Error deleting file " + f.Name + ". Exception: " + exc);
                            }
                        }
                    }

                    //load description files
                    foreach (var dfd in GetDescriptionFilesAndDescriptors(pluginFolder))
                    {
                        var descriptionFile = dfd.Key;
                        var pluginDescriptor = dfd.Value;

                        //ensure that version of plugin is valid
                        if (!pluginDescriptor.SupportedVersions.Contains(NopVersion.CurrentVersion, StringComparer.InvariantCultureIgnoreCase))
                        {
                            incompatiblePlugins.Add(pluginDescriptor.SystemName);
                            continue;
                        }

                        //some validation
                        if (String.IsNullOrWhiteSpace(pluginDescriptor.SystemName))
                            throw new Exception(string.Format("A plugin '{0}' has no system name. Try assigning the plugin a unique name and recompiling.", descriptionFile.FullName));
                        if (referencedPlugins.Contains(pluginDescriptor))
                            throw new Exception(string.Format("A plugin with '{0}' system name is already defined", pluginDescriptor.SystemName));

                        //set 'Installed' property
                        pluginDescriptor.Installed = installedPluginSystemNames
                            .FirstOrDefault(x => x.Equals(pluginDescriptor.SystemName, StringComparison.InvariantCultureIgnoreCase)) != null;

                        try
                        {
                            if (descriptionFile.Directory == null)
                                throw new Exception(string.Format("Directory cannot be resolved for '{0}' description file", descriptionFile.Name));
                            //get list of all DLLs in plugins (not in bin!)
                            var pluginFiles = descriptionFile.Directory.GetFiles("*.dll", SearchOption.AllDirectories)
                                //just make sure we're not registering shadow copied plugins
                                .Where(x => !binFiles.Select(q => q.FullName).Contains(x.FullName))
                                .Where(x => IsPackagePluginFolder(x.Directory))
                                .ToList();

                            //other plugin description info
                            var mainPluginFile = pluginFiles
                                .FirstOrDefault(x => x.Name.Equals(pluginDescriptor.PluginFileName, StringComparison.InvariantCultureIgnoreCase));
                            pluginDescriptor.OriginalAssemblyFile = mainPluginFile;

                            //shadow copy main plugin file
                            pluginDescriptor.ReferencedAssembly = PerformFileDeploy(mainPluginFile);

                            //load all other referenced assemblies now
                            foreach (var plugin in pluginFiles
                                .Where(x => !x.Name.Equals(mainPluginFile.Name, StringComparison.InvariantCultureIgnoreCase))
                                .Where(x => !IsAlreadyLoaded(x)))
                                    PerformFileDeploy(plugin);
                            
                            //init plugin type (only one plugin per assembly is allowed)
                            foreach (var t in pluginDescriptor.ReferencedAssembly.GetTypes())
                                if (typeof(IPlugin).IsAssignableFrom(t))
                                    if (!t.IsInterface)
                                        if (t.IsClass && !t.IsAbstract)
                                        {
                                            pluginDescriptor.PluginType = t;
                                            break;
                                        }

                            referencedPlugins.Add(pluginDescriptor);
                        }
                        catch (ReflectionTypeLoadException ex)
                        {
                            var msg = string.Empty;
                            foreach (var e in ex.LoaderExceptions)
                                msg += e.Message + Environment.NewLine;

                            var fail = new Exception(msg, ex);
                            Debug.WriteLine(fail.Message, fail);

                            throw fail;
                        }
                    }
                }
                catch (Exception ex)
                {
                    var msg = string.Empty;
                    for (var e = ex; e != null; e = e.InnerException)
                        msg += e.Message + Environment.NewLine;

                    var fail = new Exception(msg, ex);
                    Debug.WriteLine(fail.Message, fail);

                    throw fail;
                }


                ReferencedPlugins = referencedPlugins;
                IncompatiblePlugins = incompatiblePlugins;

            }
        }

        /// <summary>
        /// Mark plugin as installed
        /// </summary>
        /// <param name="systemName">Plugin system name</param>
        public static void MarkPluginAsInstalled(string systemName)
        {
            if (String.IsNullOrEmpty(systemName))
                throw new ArgumentNullException("systemName");

            var filePath = HostingEnvironment.MapPath(InstalledPluginsFilePath);
            if (!File.Exists(filePath))
                using (File.Create(filePath))
                {
                    //we use 'using' to close the file after it's created
                }


            var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath());
            bool alreadyMarkedAsInstalled = installedPluginSystemNames
                                .FirstOrDefault(x => x.Equals(systemName, StringComparison.InvariantCultureIgnoreCase)) != null;
            if (!alreadyMarkedAsInstalled)
                installedPluginSystemNames.Add(systemName);
            PluginFileParser.SaveInstalledPluginsFile(installedPluginSystemNames,filePath);
        }

        /// <summary>
        /// Mark plugin as uninstalled
        /// </summary>
        /// <param name="systemName">Plugin system name</param>
        public static void MarkPluginAsUninstalled(string systemName)
        {
            if (String.IsNullOrEmpty(systemName))
                throw new ArgumentNullException("systemName");

            var filePath = HostingEnvironment.MapPath(InstalledPluginsFilePath);
            if (!File.Exists(filePath))
                using (File.Create(filePath))
                {
                    //we use 'using' to close the file after it's created
                }


            var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath());
            bool alreadyMarkedAsInstalled = installedPluginSystemNames
                                .FirstOrDefault(x => x.Equals(systemName, StringComparison.InvariantCultureIgnoreCase)) != null;
            if (alreadyMarkedAsInstalled)
                installedPluginSystemNames.Remove(systemName);
            PluginFileParser.SaveInstalledPluginsFile(installedPluginSystemNames,filePath);
        }

        /// <summary>
        /// Mark plugin as uninstalled
        /// </summary>
        public static void MarkAllPluginsAsUninstalled()
        {
            var filePath = HostingEnvironment.MapPath(InstalledPluginsFilePath);
            if (File.Exists(filePath))
                File.Delete(filePath);
        }

        #endregion

        #region Utilities

        /// <summary>
        /// Get description files
        /// </summary>
        /// <param name="pluginFolder">Plugin direcotry info</param>
        /// <returns>Original and parsed description files</returns>
        private static IEnumerable<KeyValuePair<FileInfo, PluginDescriptor>> GetDescriptionFilesAndDescriptors(DirectoryInfo pluginFolder)
        {
            if (pluginFolder == null)
                throw new ArgumentNullException("pluginFolder");

            //create list (<file info, parsed plugin descritor>)
            var result = new List<KeyValuePair<FileInfo, PluginDescriptor>>();
            //add display order and path to list
            foreach (var descriptionFile in pluginFolder.GetFiles("Description.txt", SearchOption.AllDirectories))
            {
                if (!IsPackagePluginFolder(descriptionFile.Directory))
                    continue;

                //parse file
                var pluginDescriptor = PluginFileParser.ParsePluginDescriptionFile(descriptionFile.FullName);

                //populate list
                result.Add(new KeyValuePair<FileInfo, PluginDescriptor>(descriptionFile, pluginDescriptor));
            }

            //sort list by display order. NOTE: Lowest DisplayOrder will be first i.e 0 , 1, 1, 1, 5, 10
            //it's required: http://www.nopcommerce.com/boards/t/17455/load-plugins-based-on-their-displayorder-on-startup.aspx
            result.Sort((firstPair, nextPair) => firstPair.Value.DisplayOrder.CompareTo(nextPair.Value.DisplayOrder));
            return result;
        }

        /// <summary>
        /// Indicates whether assembly file is already loaded
        /// </summary>
        /// <param name="fileInfo">File info</param>
        /// <returns>Result</returns>
        private static bool IsAlreadyLoaded(FileInfo fileInfo)
        {
            //compare full assembly name
            //var fileAssemblyName = AssemblyName.GetAssemblyName(fileInfo.FullName);
            //foreach (var a in AppDomain.CurrentDomain.GetAssemblies())
            //{
            //    if (a.FullName.Equals(fileAssemblyName.FullName, StringComparison.InvariantCultureIgnoreCase))
            //        return true;
            //}
            //return false;

            //do not compare the full assembly name, just filename
            try
            {
                string fileNameWithoutExt = Path.GetFileNameWithoutExtension(fileInfo.FullName);
                if (fileNameWithoutExt == null)
                    throw new Exception(string.Format("Cannot get file extnension for {0}", fileInfo.Name));
                foreach (var a in AppDomain.CurrentDomain.GetAssemblies())
                {
                    string assemblyName = a.FullName.Split(new[] { ',' }).FirstOrDefault();
                    if (fileNameWithoutExt.Equals(assemblyName, StringComparison.InvariantCultureIgnoreCase))
                        return true;
                }
            }
            catch (Exception exc)
            {
                Debug.WriteLine("Cannot validate whether an assembly is already loaded. " + exc);
            }
            return false;
        }

        /// <summary>
        /// Perform file deply
        /// </summary>
        /// <param name="plug">Plugin file info</param>
        /// <returns>Assembly</returns>
        private static Assembly PerformFileDeploy(FileInfo plug)
        {
            if (plug.Directory.Parent == null)
                throw new InvalidOperationException("The plugin directory for the " + plug.Name +
                                                    " file exists in a folder outside of the allowed nopCommerce folder heirarchy");

            FileInfo shadowCopiedPlug;

            if (CommonHelper.GetTrustLevel() != AspNetHostingPermissionLevel.Unrestricted)
            {
                //all plugins will need to be copied to ~/Plugins/bin/
                //this is aboslutely required because all of this relies on probingPaths being set statically in the web.config
                
                //were running in med trust, so copy to custom bin folder
                var shadowCopyPlugFolder = Directory.CreateDirectory(_shadowCopyFolder.FullName);
                shadowCopiedPlug = InitializeMediumTrust(plug, shadowCopyPlugFolder);
            }
            else
            {
                var directory = AppDomain.CurrentDomain.DynamicDirectory;
                Debug.WriteLine(plug.FullName + " to " + directory);
                //were running in full trust so copy to standard dynamic folder
                shadowCopiedPlug = InitializeFullTrust(plug, new DirectoryInfo(directory));
            }

            //we can now register the plugin definition
            var shadowCopiedAssembly = Assembly.Load(AssemblyName.GetAssemblyName(shadowCopiedPlug.FullName));

            //add the reference to the build manager
            Debug.WriteLine("Adding to BuildManager: '{0}'", shadowCopiedAssembly.FullName);
            BuildManager.AddReferencedAssembly(shadowCopiedAssembly);

            return shadowCopiedAssembly;
        }

        /// <summary>
        /// Used to initialize plugins when running in Full Trust
        /// </summary>
        /// <param name="plug"></param>
        /// <param name="shadowCopyPlugFolder"></param>
        /// <returns></returns>
        private static FileInfo InitializeFullTrust(FileInfo plug, DirectoryInfo shadowCopyPlugFolder)
        {
            var shadowCopiedPlug = new FileInfo(Path.Combine(shadowCopyPlugFolder.FullName, plug.Name));
            try
            {
                File.Copy(plug.FullName, shadowCopiedPlug.FullName, true);
            }
            catch (IOException)
            {
                Debug.WriteLine(shadowCopiedPlug.FullName + " is locked, attempting to rename");
                //this occurs when the files are locked,
                //for some reason devenv locks plugin files some times and for another crazy reason you are allowed to rename them
                //which releases the lock, so that it what we are doing here, once it's renamed, we can re-shadow copy
                try
                {
                    var oldFile = shadowCopiedPlug.FullName + Guid.NewGuid().ToString("N") + ".old";
                    File.Move(shadowCopiedPlug.FullName, oldFile);
                }
                catch (IOException exc)
                {
                    throw new IOException(shadowCopiedPlug.FullName + " rename failed, cannot initialize plugin", exc);
                }
                //ok, we've made it this far, now retry the shadow copy
                File.Copy(plug.FullName, shadowCopiedPlug.FullName, true);
            }
            return shadowCopiedPlug;
        }

        /// <summary>
        /// Used to initialize plugins when running in Medium Trust
        /// </summary>
        /// <param name="plug"></param>
        /// <param name="shadowCopyPlugFolder"></param>
        /// <returns></returns>
        private static FileInfo InitializeMediumTrust(FileInfo plug, DirectoryInfo shadowCopyPlugFolder)
        {
            var shouldCopy = true;
            var shadowCopiedPlug = new FileInfo(Path.Combine(shadowCopyPlugFolder.FullName, plug.Name));

            //check if a shadow copied file already exists and if it does, check if it's updated, if not don't copy
            if (shadowCopiedPlug.Exists)
            {
                //it's better to use LastWriteTimeUTC, but not all file systems have this property
                //maybe it is better to compare file hash?
                var areFilesIdentical = shadowCopiedPlug.CreationTimeUtc.Ticks >= plug.CreationTimeUtc.Ticks;
                if (areFilesIdentical)
                {
                    Debug.WriteLine("Not copying; files appear identical: '{0}'", shadowCopiedPlug.Name);
                    shouldCopy = false;
                }
                else
                {
                    //delete an existing file

                    //More info: http://www.nopcommerce.com/boards/t/11511/access-error-nopplugindiscountrulesbillingcountrydll.aspx?p=4#60838
                    Debug.WriteLine("New plugin found; Deleting the old file: '{0}'", shadowCopiedPlug.Name);
                    File.Delete(shadowCopiedPlug.FullName);
                }
            }

            if (shouldCopy)
            {
                try
                {
                    File.Copy(plug.FullName, shadowCopiedPlug.FullName, true);
                }
                catch (IOException)
                {
                    Debug.WriteLine(shadowCopiedPlug.FullName + " is locked, attempting to rename");
                    //this occurs when the files are locked,
                    //for some reason devenv locks plugin files some times and for another crazy reason you are allowed to rename them
                    //which releases the lock, so that it what we are doing here, once it's renamed, we can re-shadow copy
                    try
                    {
                        var oldFile = shadowCopiedPlug.FullName + Guid.NewGuid().ToString("N") + ".old";
                        File.Move(shadowCopiedPlug.FullName, oldFile);
                    }
                    catch (IOException exc)
                    {
                        throw new IOException(shadowCopiedPlug.FullName + " rename failed, cannot initialize plugin", exc);
                    }
                    //ok, we've made it this far, now retry the shadow copy
                    File.Copy(plug.FullName, shadowCopiedPlug.FullName, true);
                }
            }

            return shadowCopiedPlug;
        }
        
        /// <summary>
        /// Determines if the folder is a bin plugin folder for a package
        /// </summary>
        /// <param name="folder"></param>
        /// <returns></returns>
        private static bool IsPackagePluginFolder(DirectoryInfo folder)
        {
            if (folder == null) return false;
            if (folder.Parent == null) return false;
            if (!folder.Parent.Name.Equals("Plugins", StringComparison.InvariantCultureIgnoreCase)) return false;
            return true;
        }

        /// <summary>
        /// Gets the full path of InstalledPlugins.txt file
        /// </summary>
        /// <returns></returns>
        private static string GetInstalledPluginsFilePath()
        { 
            var filePath = HostingEnvironment.MapPath(InstalledPluginsFilePath);
            return filePath;
        }

        #endregion
    }
}

从注释可以看到 他是参考了Umbraco。

调用了

/// <summary>
        /// Returns a collection of all referenced plugin assemblies that have been shadow copied
        /// </summary>
        public static IEnumerable<PluginDescriptor> ReferencedPlugins { get; set; }

Initialize方法应该对他进行了设置,看它都做了什么:

public static void Initialize()
        {
            using (new WriteLockDisposable(Locker))
            {
                // TODO: Add verbose exception handling / raising here since this is happening on app startup and could
                // prevent app from starting altogether
                var pluginFolder = new DirectoryInfo(HostingEnvironment.MapPath(PluginsPath));
                _shadowCopyFolder = new DirectoryInfo(HostingEnvironment.MapPath(ShadowCopyPath));

                var referencedPlugins = new List<PluginDescriptor>();
                var incompatiblePlugins = new List<string>();

                _clearShadowDirectoryOnStartup = !String.IsNullOrEmpty(ConfigurationManager.AppSettings["ClearPluginsShadowDirectoryOnStartup"]) &&
                   Convert.ToBoolean(ConfigurationManager.AppSettings["ClearPluginsShadowDirectoryOnStartup"]);

                try
                {
                    var installedPluginSystemNames = PluginFileParser.ParseInstalledPluginsFile(GetInstalledPluginsFilePath());

                    Debug.WriteLine("Creating shadow copy folder and querying for dlls");
                    //ensure folders are created
                    Directory.CreateDirectory(pluginFolder.FullName);
                    Directory.CreateDirectory(_shadowCopyFolder.FullName);

                    //get list of all files in bin
                    var binFiles = _shadowCopyFolder.GetFiles("*", SearchOption.AllDirectories);
                    if (_clearShadowDirectoryOnStartup)
                    {
                        //clear out shadow copied plugins
                        foreach (var f in binFiles)
                        {
                            Debug.WriteLine("Deleting " + f.Name);
                            try
                            {
                                File.Delete(f.FullName);
                            }
                            catch (Exception exc)
                            {
                                Debug.WriteLine("Error deleting file " + f.Name + ". Exception: " + exc);
                            }
                        }
                    }

                    //load description files
                    foreach (var dfd in GetDescriptionFilesAndDescriptors(pluginFolder))
                    {
                        var descriptionFile = dfd.Key;
                        var pluginDescriptor = dfd.Value;

                        //ensure that version of plugin is valid
                        if (!pluginDescriptor.SupportedVersions.Contains(NopVersion.CurrentVersion, StringComparer.InvariantCultureIgnoreCase))
                        {
                            incompatiblePlugins.Add(pluginDescriptor.SystemName);
                            continue;
                        }

                        //some validation
                        if (String.IsNullOrWhiteSpace(pluginDescriptor.SystemName))
                            throw new Exception(string.Format("A plugin '{0}' has no system name. Try assigning the plugin a unique name and recompiling.", descriptionFile.FullName));
                        if (referencedPlugins.Contains(pluginDescriptor))
                            throw new Exception(string.Format("A plugin with '{0}' system name is already defined", pluginDescriptor.SystemName));

                        //set 'Installed' property
                        pluginDescriptor.Installed = installedPluginSystemNames
                            .FirstOrDefault(x => x.Equals(pluginDescriptor.SystemName, StringComparison.InvariantCultureIgnoreCase)) != null;

                        try
                        {
                            if (descriptionFile.Directory == null)
                                throw new Exception(string.Format("Directory cannot be resolved for '{0}' description file", descriptionFile.Name));
                            //get list of all DLLs in plugins (not in bin!)
                            var pluginFiles = descriptionFile.Directory.GetFiles("*.dll", SearchOption.AllDirectories)
                                //just make sure we're not registering shadow copied plugins
                                .Where(x => !binFiles.Select(q => q.FullName).Contains(x.FullName))
                                .Where(x => IsPackagePluginFolder(x.Directory))
                                .ToList();

                            //other plugin description info
                            var mainPluginFile = pluginFiles
                                .FirstOrDefault(x => x.Name.Equals(pluginDescriptor.PluginFileName, StringComparison.InvariantCultureIgnoreCase));
                            pluginDescriptor.OriginalAssemblyFile = mainPluginFile;

                            //shadow copy main plugin file
                            pluginDescriptor.ReferencedAssembly = PerformFileDeploy(mainPluginFile);

                            //load all other referenced assemblies now
                            foreach (var plugin in pluginFiles
                                .Where(x => !x.Name.Equals(mainPluginFile.Name, StringComparison.InvariantCultureIgnoreCase))
                                .Where(x => !IsAlreadyLoaded(x)))
                                    PerformFileDeploy(plugin);
                            
                            //init plugin type (only one plugin per assembly is allowed)
                            foreach (var t in pluginDescriptor.ReferencedAssembly.GetTypes())
                                if (typeof(IPlugin).IsAssignableFrom(t))
                                    if (!t.IsInterface)
                                        if (t.IsClass && !t.IsAbstract)
                                        {
                                            pluginDescriptor.PluginType = t;
                                            break;
                                        }

                            referencedPlugins.Add(pluginDescriptor);
                        }
                        catch (ReflectionTypeLoadException ex)
                        {
                            var msg = string.Empty;
                            foreach (var e in ex.LoaderExceptions)
                                msg += e.Message + Environment.NewLine;

                            var fail = new Exception(msg, ex);
                            Debug.WriteLine(fail.Message, fail);

                            throw fail;
                        }
                    }
                }
                catch (Exception ex)
                {
                    var msg = string.Empty;
                    for (var e = ex; e != null; e = e.InnerException)
                        msg += e.Message + Environment.NewLine;

                    var fail = new Exception(msg, ex);
                    Debug.WriteLine(fail.Message, fail);

                    throw fail;
                }


                ReferencedPlugins = referencedPlugins;
                IncompatiblePlugins = incompatiblePlugins;

            }
        }

try catch内部  根据 private const string InstalledPluginsFilePath = "~/App_Data/InstalledPlugins.txt"; 获得已安装插件名字的LIST<STRING>.

获得启动时清除目录为false。

调用GetDescriptionFilesAndDescriptors方法。:

/// <summary>
        /// Get description files
        /// </summary>
        /// <param name="pluginFolder">Plugin direcotry info</param>
        /// <returns>Original and parsed description files</returns>
        private static IEnumerable<KeyValuePair<FileInfo, PluginDescriptor>> GetDescriptionFilesAndDescriptors(DirectoryInfo pluginFolder)
        {
            if (pluginFolder == null)
                throw new ArgumentNullException("pluginFolder");

            //create list (<file info, parsed plugin descritor>)
            var result = new List<KeyValuePair<FileInfo, PluginDescriptor>>();
            //add display order and path to list
            foreach (var descriptionFile in pluginFolder.GetFiles("Description.txt", SearchOption.AllDirectories))
            {
                if (!IsPackagePluginFolder(descriptionFile.Directory))
                    continue;

                //parse file
                var pluginDescriptor = PluginFileParser.ParsePluginDescriptionFile(descriptionFile.FullName);

                //populate list
                result.Add(new KeyValuePair<FileInfo, PluginDescriptor>(descriptionFile, pluginDescriptor));
            }

            //sort list by display order. NOTE: Lowest DisplayOrder will be first i.e 0 , 1, 1, 1, 5, 10
            //it's required: http://www.nopcommerce.com/boards/t/17455/load-plugins-based-on-their-displayorder-on-startup.aspx
            result.Sort((firstPair, nextPair) => firstPair.Value.DisplayOrder.CompareTo(nextPair.Value.DisplayOrder));
            return result;
        }

创建一个键值对单元类的List集合。

获取pluginFolder下的所有Description .txt文件,遍历。。:

/// <summary>
        /// Determines if the folder is a bin plugin folder for a package
        /// </summary>
        /// <param name="folder"></param>
        /// <returns></returns>
        private static bool IsPackagePluginFolder(DirectoryInfo folder)
        {
            if (folder == null) return false;
            if (folder.Parent == null) return false;
            if (!folder.Parent.Name.Equals("Plugins", StringComparison.InvariantCultureIgnoreCase)) return false;
            return true;
        }

就是确保 这个文件夹是plugin的直接子文件夹。

然后获得插件描述文件:

public static PluginDescriptor ParsePluginDescriptionFile(string filePath)
        {
            var descriptor = new PluginDescriptor();
            var text = File.ReadAllText(filePath);
            if (String.IsNullOrEmpty(text))
                return descriptor;

            var settings = new List<string>();
            using (var reader = new StringReader(text))
            {
                string str;
                while ((str = reader.ReadLine()) != null)
                {
                    if (String.IsNullOrWhiteSpace(str))
                        continue;
                    settings.Add(str.Trim());
                }
            }

            //Old way of file reading. This leads to unexpected behavior when a user's FTP program transfers these files as ASCII (\r\n becomes \n).
            //var settings = text.Split(new[] { Environment.NewLine }, StringSplitOptions.RemoveEmptyEntries);

            foreach (var setting in settings)
            {
                var separatorIndex = setting.IndexOf(':');
                if (separatorIndex == -1)
                {
                    continue;
                }
                string key = setting.Substring(0, separatorIndex).Trim();
                string value = setting.Substring(separatorIndex + 1).Trim();

                switch (key)
                {
                    case "Group":
                        descriptor.Group = value;
                        break;
                    case "FriendlyName":
                        descriptor.FriendlyName = value;
                        break;
                    case "SystemName":
                        descriptor.SystemName = value;
                        break;
                    case "Version":
                        descriptor.Version = value;
                        break;
                    case "SupportedVersions":
                        {
                            //parse supported versions
                            descriptor.SupportedVersions = value.Split(new [] { ',' }, StringSplitOptions.RemoveEmptyEntries)
                                .Select(x => x.Trim())
                                .ToList();
                        }
                        break;
                    case "Author":
                        descriptor.Author = value;
                        break;
                    case "DisplayOrder":
                        {
                            int displayOrder;
                            int.TryParse(value, out displayOrder);
                            descriptor.DisplayOrder = displayOrder;
                        }
                        break;
                    case "FileName":
                        descriptor.PluginFileName = value;
                        break;
                    case "LimitedToStores":
                        {
                            //parse list of store IDs
                            foreach (var str1 in value.Split(new [] {','}, StringSplitOptions.RemoveEmptyEntries)
                                                      .Select(x => x.Trim()))
                            {
                                int storeId;
                                if (int.TryParse(str1, out storeId))
                                {
                                    descriptor.LimitedToStores.Add(storeId);
                                }
                            }
                        }
                        break;
                    default:
                        break;
                }
            }

            //nopCommerce 2.00 didn't have 'SupportedVersions' parameter
            //so let's set it to "2.00"
            if (descriptor.SupportedVersions.Count == 0)
                descriptor.SupportedVersions.Add("2.00");

            return descriptor;
        }

最后根据DisplayOrder排序   返回List.

循环List根据值 ,如果不包含当前版本号,则加入到不兼容列表,并continue.

然后验证 要有systemName,并插件没哟重复。

然后根据安装文件LIST<STRING>列表查找是否已安装。

获取所有的plugin目录的DLL文件列表,并且不再BIN目录中,而且是直接子目录。

根据上步的列表找出与pluginDescriptor.PluginFileName同名的DLL文件。

然后赋值:

pluginDescriptor.OriginalAssemblyFile = mainPluginFile;

                            //shadow copy main plugin file
                            pluginDescriptor.ReferencedAssembly = PerformFileDeploy(mainPluginFile);
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