标签：attr abstract 扩展 用户 npe 编译 string space var
纸壳CMS是一个开源的可视化设计CMS，通过拖拽，在线编辑的方式来创建网站。
https://github.com/SeriaWei/ZKEACMS.Core
欢迎Star，Fork，发PR。:)
纸壳CMS是基于插件化设计的，可以通过扩展插件来实现不同的功能。如何通过插件来扩展，可以参考这篇文章：
http://www.zkea.net/codesnippet/detail/zkeacms-plugin-development.html
纸壳CMS的插件是相互独立的，各插件的引用也相互独立，即各插件都可引用各自需要的nuget包来达到目的。而不用把引用加到底层。
纸壳CMS的插件的存放目录在开发环境和已发布的程序中是不一样的。在开发环境，插件和其它的项目统一放在src目录下：
而发布程序以后，插件会在wwwroot/Plugins目录下：
所以，如果在开发过程中要使用插件目录时，需要使用特定的方法来获取真实的目录，如：
PluginBase.GetPath<SectionPlug>()
有关插件用到的所有相关代码，都在 EasyFrameWork/Mvc/Plugin 目录下：
纸壳CMS在程序启动时加载所有启用的插件Loader.cs：
public IEnumerable<IPluginStartup> LoadEnablePlugins(IServiceCollection serviceCollection) { var start = DateTime.Now; Loaders.AddRange(GetPlugins().Where(m => m.Enable && m.ID.IsNotNullAndWhiteSpace()).Select(m => { var loader = new AssemblyLoader(); loader.CurrentPath = m.RelativePath; var assemblyPath = Path.Combine(m.RelativePath, (HostingEnvironment.IsDevelopment() ? Path.Combine(AltDevelopmentPath) : string.Empty), m.FileName); Console.WriteLine("Loading: {0}", m.Name); var assemblies = loader.LoadPlugin(assemblyPath); assemblies.Each(assembly => { if (!LoadedAssemblies.ContainsKey(assembly.FullName)) { LoadedAssemblies.Add(assembly.FullName, assembly); } }); return loader; })); Console.WriteLine("All plugins are loaded. Elapsed: {0}ms", (DateTime.Now - start).Milliseconds); return serviceCollection.ConfigurePlugin().BuildServiceProvider().GetPlugins(); }
AssemblyLoader是加载插件DLL的关键，纸壳CMS主要通过它来加载插件，并加载插件的相关依赖，并注册插件。
namespace Easy.Mvc.Plugin { public class AssemblyLoader { private const string ControllerTypeNameSuffix = "Controller"; private static bool Resolving { get; set; } public AssemblyLoader() { DependencyAssemblies = new List<Assembly>(); } public string CurrentPath { get; set; } public string AssemblyPath { get; set; } public Assembly CurrentAssembly { get; private set; } public List<Assembly> DependencyAssemblies { get; private set; } private TypeInfo PluginTypeInfo = typeof(IPluginStartup).GetTypeInfo(); public IEnumerable<Assembly> LoadPlugin(string path) { if (CurrentAssembly == null) { AssemblyPath = path; CurrentAssembly = AssemblyLoadContext.Default.LoadFromAssemblyPath(path); ResolveDenpendency(CurrentAssembly); RegistAssembly(CurrentAssembly); yield return CurrentAssembly; foreach (var item in DependencyAssemblies) { yield return item; } } else { throw new Exception("A loader just can load one assembly."); } } private void ResolveDenpendency(Assembly assembly) { string currentName = assembly.GetName().Name; var dependencyCompilationLibrary = DependencyContext.Load(assembly) .CompileLibraries.Where(de => de.Name != currentName && !DependencyContext.Default.CompileLibraries.Any(m => m.Name == de.Name)) .ToList(); dependencyCompilationLibrary.Each(libaray => { bool depLoaded = false; foreach (var item in libaray.Assemblies) { var files = new DirectoryInfo(Path.GetDirectoryName(assembly.Location)).GetFiles(Path.GetFileName(item)); foreach (var file in files) { DependencyAssemblies.Add(AssemblyLoadContext.Default.LoadFromAssemblyPath(file.FullName)); depLoaded = true; break; } } if (!depLoaded) { foreach (var item in libaray.ResolveReferencePaths()) { if (File.Exists(item)) { DependencyAssemblies.Add(AssemblyLoadContext.Default.LoadFromAssemblyPath(item)); break; } } } }); } private void RegistAssembly(Assembly assembly) { List<TypeInfo> controllers = new List<TypeInfo>(); PluginDescriptor plugin = null; foreach (var typeInfo in assembly.DefinedTypes) { if (typeInfo.IsAbstract || typeInfo.IsInterface) continue; if (IsController(typeInfo) && !controllers.Contains(typeInfo)) { controllers.Add(typeInfo); } else if (PluginTypeInfo.IsAssignableFrom(typeInfo)) { plugin = new PluginDescriptor(); plugin.PluginType = typeInfo.AsType(); plugin.Assembly = assembly; plugin.CurrentPluginPath = CurrentPath; } } if (controllers.Count > 0 && !ActionDescriptorProvider.PluginControllers.ContainsKey(assembly.FullName)) { ActionDescriptorProvider.PluginControllers.Add(assembly.FullName, controllers); } if (plugin != null) { PluginActivtor.LoadedPlugins.Add(plugin); } } protected bool IsController(TypeInfo typeInfo) { if (!typeInfo.IsClass) { return false; } if (typeInfo.IsAbstract) { return false; } if (!typeInfo.IsPublic) { return false; } if (typeInfo.ContainsGenericParameters) { return false; } if (typeInfo.IsDefined(typeof(NonControllerAttribute))) { return false; } if (!typeInfo.Name.EndsWith(ControllerTypeNameSuffix, StringComparison.OrdinalIgnoreCase) && !typeInfo.IsDefined(typeof(ControllerAttribute))) { return false; } return true; } } }
注册插件时，需要将插件中的所有Controller分析出来，当用户访问到插件的对应Controller时，才可以实例化Controller并调用。
ASP.NET MVC 的视图（cshtml）是可以动态编译的。但由于插件是动态加载的，编译器并不知道编译视图所需要的引用在什么地方，这会导致插件中的视图编译失败。并且程序也需要告诉编译器到哪里去找这个视图。PluginRazorViewEngineOptionsSetup.cs 便起到了这个作用。
由于开发环境的目录不同，对以针对开发环境，需要一个视图文件提供程序来解析视图文件位置：
if (hostingEnvironment.IsDevelopment()) { options.FileProviders.Add(new DeveloperViewFileProvider(hostingEnvironment)); } loader.GetPlugins().Where(m => m.Enable && m.ID.IsNotNullAndWhiteSpace()).Each(m => { var directory = new DirectoryInfo(m.RelativePath); if (hostingEnvironment.IsDevelopment()) { options.ViewLocationFormats.Add($"{DeveloperViewFileProvider.ProjectRootPath}{directory.Name}" + "/Views/{1}/{0}" + RazorViewEngine.ViewExtension); options.ViewLocationFormats.Add($"{DeveloperViewFileProvider.ProjectRootPath}{directory.Name}" + "/Views/Shared/{0}" + RazorViewEngine.ViewExtension); options.ViewLocationFormats.Add($"{DeveloperViewFileProvider.ProjectRootPath}{directory.Name}" + "/Views/{0}" + RazorViewEngine.ViewExtension); } else { options.ViewLocationFormats.Add($"/wwwroot/{Loader.PluginFolder}/{directory.Name}" + "/Views/{1}/{0}" + RazorViewEngine.ViewExtension); options.ViewLocationFormats.Add($"/wwwroot/{Loader.PluginFolder}/{directory.Name}" + "/Views/Shared/{0}" + RazorViewEngine.ViewExtension); options.ViewLocationFormats.Add($"/wwwroot/{Loader.PluginFolder}/{directory.Name}" + "/Views/{0}" + RazorViewEngine.ViewExtension); } }); options.ViewLocationFormats.Add("/Views/{0}" + RazorViewEngine.ViewExtension);
为了解决引用问题，需要把插件相关的所有引用都加入到编译环境中：
loader.GetPluginAssemblies().Each(assembly => { var reference = MetadataReference.CreateFromFile(assembly.Location); options.AdditionalCompilationReferences.Add(reference); });
标签：attr abstract 扩展 用户 npe 编译 string space var
原文地址：https://www.cnblogs.com/seriawei/p/9537867.html
