(五)学习了解OrchardCore笔记——灵魂中间件ModularTenantContainerMiddleware的第一行②模块的功能部分

　　在(三)的时候已经说到模块集合用ForEachAsync的扩展方法分配多个任务，把每个modules的ManifestInfo分析出来的功能加入ConcurrentDictionary。我们先看看这个扩展方法：

public static class EnumerableExtensions
    {
        public static Task ForEachAsync(this IEnumerable source, Func body)
        {
            var partitionCount = System.Environment.ProcessorCount;

            return Task.WhenAll(
                from partition in Partitioner.Create(source).GetPartitions(partitionCount)
                select Task.Run(async delegate
                {
                    using (partition)
                    {
                        while (partition.MoveNext())
                        {
                            await body(partition.Current);
                        }
                    }
                }));
        }
    }

　　这个查下msdn就非常简单明了，partitionCount获取可用逻辑处理器的数量(网上也有说是一组逻辑处理器的数量，一组的区别是有的服务器cpu是多组核心构成的，clr只能在一组逻辑处理器运行？也有人说现在已经可以运行在该服务器所有逻辑处理器上了，这点我不清楚，因为我没有这么多核心的处理器可以测试，这里当作所有逻辑处理器吧)。然后Partitioner.Create(source)就是把模块集合创建成可排序的程序分区，GetPartitions(partitionCount)就是按逻辑处理器的数量分区，然后开始按分区执行任务，看看partition.MoveNext()就是每个分区都是一个接着一个执行到最后一个集合的元素(Task.WhenAll和Task.Run这个不用说估计大家都懂，不懂自己msdn)，partition.Current就是当前位置的元素。body就是委托，因此可以清晰的知道ForEachAsync就是把modules集合按逻辑处理器分区然后迭代执行委托，天啊，我只会foreach，这种多线程操作我也是第一次见。

　　返回ExtensionManager类继续看看ForEachAsync这部分代码

　　　　　　　　　　// Load all extensions in parallel
                await modules.ForEachAsync((module) =>
                {
                    if (!module.ModuleInfo.Exists)
                    {
                        return Task.CompletedTask;
                    }
                    var manifestInfo = new ManifestInfo(module.ModuleInfo);

                    var extensionInfo = new ExtensionInfo(module.SubPath, manifestInfo, (mi, ei) =>
                    {
                        return _featuresProvider.GetFeatures(ei, mi);
                    });

                    var entry = new ExtensionEntry
                    {
                        ExtensionInfo = extensionInfo,
                        Assembly = module.Assembly,
                        ExportedTypes = module.Assembly.ExportedTypes
                    };

                    loadedExtensions.TryAdd(module.Name, entry);

                    return Task.CompletedTask;
                });

　　每个modules集合的元素都执行一遍ForEachAsync里面的委托(我还是喜欢c里面指针函数的叫法，因为明显就是个函数吗)。看看这个函数不对是委托，传入参数就是具体的某一个module，先判断module.ModuleInfo是否存在，之前篇幅没说这个module.ModuleInfo其实就是每个模块项目(包括主题项目)里面的Manifest.cs文件映射到类，看看Module的构造函数就很清楚了(在(三)里面Application实例化中第二个参数里面GetModules()添加Module的时候)。也就是说以后自定义模块必须包含这个文件，不然不会加载进来。接下来就实例化该模块的扩展信息类extensionInfo，这个类很简单，我们看看ExtensionInfo的代码：

    public class ExtensionInfo : IExtensionInfo
    {
        public ExtensionInfo(
            string subPath,
            IManifestInfo manifestInfo,
            Func> features)
        {
            SubPath = subPath;
            Manifest = manifestInfo;
            Features = features(manifestInfo, this);
        }

        public string Id => Manifest.ModuleInfo.Id;
        public string SubPath { get; }
        public IManifestInfo Manifest { get; }
        public IEnumerable Features { get; }
        public bool Exists => Manifest.Exists;
    }

　　里面主要几个属性((三)里没追踪Modules自己追踪下很清楚这些属性的值是什么)。构造函数传入的三个参数也很明了就是实例化给属性赋值。1、SubPath模块的路径，自己点下很清晰就是Areas/模块名，这个很属性吧，没错，跟asp.net core的区域一样。2、Manifest模块的Manifest.cs文件反射出的类。3、调用这个委托给功能集合赋值。我们看看这个委托实现的代码(跟ExtensionManager同个目录下有个Features目录的FeaturesProvider类)：

　　

　　 public class FeaturesProvider : IFeaturesProvider
    {
        public const string FeatureProviderCacheKey = "FeatureProvider:Features";

        private readonly IEnumerable _featureBuilderEvents;

        public FeaturesProvider(IEnumerable featureBuilderEvents)
        {
            _featureBuilderEvents = featureBuilderEvents;
        }

        public IEnumerable GetFeatures(
            IExtensionInfo extensionInfo,
            IManifestInfo manifestInfo)
        {
            var featuresInfos = new List();

            // Features and Dependencies live within this section
            var features = manifestInfo.ModuleInfo.Features.ToList();
            if (features.Count > 0)
            {
                foreach (var feature in features)
                {
                    if (String.IsNullOrWhiteSpace(feature.Id))
                    {
                        throw new ArgumentException(
                            $"A feature is missing a mandatory 'Id' property in the Module '{extensionInfo.Id}'");
                    }

                    var featureId = feature.Id;
                    var featureName = feature.Name ?? feature.Id;

                    var featureDependencyIds = feature.Dependencies
                        .Select(e => e.Trim()).ToArray();

                    if (!int.TryParse(feature.Priority ?? manifestInfo.ModuleInfo.Priority, out int featurePriority))
                    {
                        featurePriority = 0;
                    }

                    var featureCategory = feature.Category ?? manifestInfo.ModuleInfo.Category;
                    var featureDescription = feature.Description ?? manifestInfo.ModuleInfo.Description;
                    var featureDefaultTenantOnly = feature.DefaultTenantOnly;
                    var featureIsAlwaysEnabled = feature.IsAlwaysEnabled;

                    var context = new FeatureBuildingContext
                    {
                        FeatureId = featureId,
                        FeatureName = featureName,
                        Category = featureCategory,
                        Description = featureDescription,
                        ExtensionInfo = extensionInfo,
                        ManifestInfo = manifestInfo,
                        Priority = featurePriority,
                        FeatureDependencyIds = featureDependencyIds,
                        DefaultTenantOnly = featureDefaultTenantOnly,
                        IsAlwaysEnabled = featureIsAlwaysEnabled
                    };

                    foreach (var builder in _featureBuilderEvents)
                    {
                        builder.Building(context);
                    }

                    var featureInfo = new FeatureInfo(
                        featureId,
                        featureName,
                        featurePriority,
                        featureCategory,
                        featureDescription,
                        extensionInfo,
                        featureDependencyIds,
                        featureDefaultTenantOnly,
                        featureIsAlwaysEnabled);

                    foreach (var builder in _featureBuilderEvents)
                    {
                        builder.Built(featureInfo);
                    }

                    featuresInfos.Add(featureInfo);
                }
            }
            else
            {
                // The Extension has only one feature, itself, and that can have dependencies
                var featureId = extensionInfo.Id;
                var featureName = manifestInfo.Name;

                var featureDependencyIds = manifestInfo.ModuleInfo.Dependencies
                    .Select(e => e.Trim()).ToArray();

                if (!int.TryParse(manifestInfo.ModuleInfo.Priority, out int featurePriority))
                {
                    featurePriority = 0;
                }

                var featureCategory = manifestInfo.ModuleInfo.Category;
                var featureDescription = manifestInfo.ModuleInfo.Description;
                var featureDefaultTenantOnly = manifestInfo.ModuleInfo.DefaultTenantOnly;
                var featureIsAlwaysEnabled = manifestInfo.ModuleInfo.IsAlwaysEnabled;

                var context = new FeatureBuildingContext
                {
                    FeatureId = featureId,
                    FeatureName = featureName,
                    Category = featureCategory,
                    Description = featureDescription,
                    ExtensionInfo = extensionInfo,
                    ManifestInfo = manifestInfo,
                    Priority = featurePriority,
                    FeatureDependencyIds = featureDependencyIds,
                    DefaultTenantOnly = featureDefaultTenantOnly,
                    IsAlwaysEnabled = featureIsAlwaysEnabled
                };

                foreach (var builder in _featureBuilderEvents)
                {
                    builder.Building(context);
                }

                var featureInfo = new FeatureInfo(
                    context.FeatureId,
                    context.FeatureName,
                    context.Priority,
                    context.Category,
                    context.Description,
                    context.ExtensionInfo,
                    context.FeatureDependencyIds,
                    context.DefaultTenantOnly,
                    context.IsAlwaysEnabled);

                foreach (var builder in _featureBuilderEvents)
                {
                    builder.Built(featureInfo);
                }

                featuresInfos.Add(featureInfo);
            }

            return featuresInfos;
        }
    }

　　看起来有点长，其实没啥说的，基本都在赋值，构造函数通过依赖注入解决，略过。直接看看委托的方法GetFeatures(IExtensionInfo extensionInfo,IManifestInfo manifestInfo)，两个参数就是刚刚那个扩展信息和对应的mainfest.cs所反射的类。创建要返回的功能列表信息集合var featuresInfos = new List()。然后获取该模块依赖的功能集合var features = manifestInfo.ModuleInfo.Features.ToList()，官网也说了一个模块可以有0到多个功能，具体就是Manifest.cs文件有没多个assembly: Feature，具体代码0个和多个并没有多大区别，你可以发现多个了用foreach把每个功能加入集合，0个就用扩展信息填充功能然后加入集合返回。这些没啥问题，然后之前好像注入了什么featureBuilderEvents在这里居然有两个方法Building和Built，它们实现的类是ThemeFeatureBuilderEvents(继承FeatureBuilderEvents，依赖注入不说也懂，直接找实现就对了，我最怕Events了，我最不了解事件，说是委托的封装，委托我直接理解成指针函数，事件这个概念我还没想好代替的说辞，其实我都是简单的理解成多个委托，毕竟事件和委托的区别就是事件可以有多个方法嘛，不对多个委托，我c#都是自学，这些概念可能表述不清楚，上学科班只教了c和java里面都没这种概念，我是计算机系但是非软件专业而是网络专业，见谅)。重写了方法Building，就是提取出主题啊(判断是否是主题)，(四)这篇说过，模块包含三个解决方案文件夹里的项目：普通模块、cms模块和主题模块(可能上篇表述不一样)。下面代码很明显就是有基础主题就修改下：

　　

    public class ThemeFeatureBuilderEvents : FeatureBuilderEvents
    {
        public override void Building(FeatureBuildingContext context)
        {
            var moduleInfo = context.ExtensionInfo.Manifest.ModuleInfo;

            if (moduleInfo is ThemeAttribute || (moduleInfo is ModuleMarkerAttribute &&
                moduleInfo.Type.Equals("Theme", StringComparison.OrdinalIgnoreCase)))
            {
                var extensionInfo = new ThemeExtensionInfo(context.ExtensionInfo);

                if (extensionInfo.HasBaseTheme())
                {
                    context.FeatureDependencyIds = context
                        .FeatureDependencyIds
                        .Concat(new[] { extensionInfo.BaseTheme })
                        .ToArray();
                }

                context.ExtensionInfo = extensionInfo;
            }
        }
    }

　　感觉第(四)篇了解过后没啥说的，后面直接跟踪就好了，是我的角度不对？怪不得别人都从架构说起，我从asp.net core按流程说中间少了点什么，有点不连贯，老是得去补充点什么，越说越乱，被我弄乱的感觉还不如直接自己追踪下源码？我看看能不能努力写到下个中间件。要我从架构上说我办不到啊，我连画uml的软件都不知道有哪些，后面学学看。