IOptions是一个接口里面只有一个Values属性，该接口通过OptionsManager实现

public interface IOptions<out TOptions> where TOptions : class, new() { /// <summary> /// The default configured <typeparamref name="TOptions"/> instance /// </summary> TOptions Value { get; } } OptionsManager

OptionsManager实现了IOptions<>和IOptionsSnapshot<>，他使用内部属性OptionsCache 进行缓存操作；实现IOptionsSnapshot接口Get(string name)其实就是获取我们第一章所指定的Name，通过IOptionsFactory<>创建TOptions实例

public class OptionsManager<TOptions> : IOptions<TOptions>, IOptionsSnapshot<TOptions> where TOptions : class, new() { private readonly IOptionsFactory<TOptions> _factory; private readonly OptionsCache<TOptions> _cache = new OptionsCache<TOptions>(); // Note: this is a private cache /// <summary> /// Initializes a new instance with the specified options configurations. /// </summary> /// <param name="factory">The factory to use to create options.</param> public OptionsManager(IOptionsFactory<TOptions> factory) { _factory = factory; } /// <summary> /// The default configured <typeparamref name="TOptions"/> instance, equivalent to Get(Options.DefaultName). /// </summary> public TOptions Value { get { return Get(Options.DefaultName); } } /// <summary> /// Returns a configured <typeparamref name="TOptions"/> instance with the given <paramref name="name"/>. /// </summary> public virtual TOptions Get(string name) { name = name ?? Options.DefaultName; // Store the options in our instance cache return _cache.GetOrAdd(name, () => _factory.Create(name)); } } public interface IOptionsSnapshot<out TOptions> : IOptions<TOptions> where TOptions : class, new() { /// <summary> /// Returns a configured <typeparamref name="TOptions"/> instance with the given name. /// </summary> TOptions Get(string name); } OptionsCache

OptionsCache采用了线程安全字典ConcurrentDictionary进行了封装用于内存缓存

public class OptionsCache<TOptions> : IOptionsMonitorCache<TOptions> where TOptions : class { private readonly ConcurrentDictionary<string, Lazy<TOptions>> _cache = new ConcurrentDictionary<string, Lazy<TOptions>>(StringComparer.Ordinal); /// <summary> /// Clears all options instances from the cache. /// </summary> public void Clear() => _cache.Clear(); /// <summary> /// Gets a named options instance, or adds a new instance created with <paramref name="createOptions"/>. /// </summary> /// <param name="name">The name of the options instance.</param> /// <param name="createOptions">The func used to create the new instance.</param> /// <returns>The options instance.</returns> public virtual TOptions GetOrAdd(string name, Func<TOptions> createOptions) { if (createOptions == null) { throw new ArgumentNullException(nameof(createOptions)); } name = name ?? Options.DefaultName; return _cache.GetOrAdd(name, new Lazy<TOptions>(createOptions)).Value; } /// <summary> /// Tries to adds a new option to the cache, will return false if the name already exists. /// </summary> /// <param name="name">The name of the options instance.</param> /// <param name="options">The options instance.</param> /// <returns>Whether anything was added.</returns> public virtual bool TryAdd(string name, TOptions options) { if (options == null) { throw new ArgumentNullException(nameof(options)); } name = name ?? Options.DefaultName; return _cache.TryAdd(name, new Lazy<TOptions>(() => options)); } /// <summary> /// Try to remove an options instance. /// </summary> /// <param name="name">The name of the options instance.</param> /// <returns>Whether anything was removed.</returns> public virtual bool TryRemove(string name) { name = name ?? Options.DefaultName; return _cache.TryRemove(name, out var ignored); } } OptionsFactory

OptionsFactory实现了 IOptionsFactory.Create(string name);,
而OptionsFactory构造函数中注入了IConfigureOptions<>和IPostConfigureOptions<>，，
这里使用了IEnumerable类型标识当注册多个时候按照次数依次的执行，从如下代码中我们也看到了我们在上一章中所说的Configures和postConfigures注册先后顺序问题。

public class OptionsFactory<TOptions> : IOptionsFactory<TOptions> where TOptions : class, new() { private readonly IEnumerable<IConfigureOptions<TOptions>> _setups; private readonly IEnumerable<IPostConfigureOptions<TOptions>> _postConfigures; private readonly IEnumerable<IValidateOptions<TOptions>> _validations; public OptionsFactory(IEnumerable<IConfigureOptions<TOptions>> setups, IEnumerable<IPostConfigureOptions<TOptions>> postConfigures) : this(setups, postConfigures, validations: null) { } public OptionsFactory(IEnumerable<IConfigureOptions<TOptions>> setups, IEnumerable<IPostConfigureOptions<TOptions>> postConfigures, IEnumerable<IValidateOptions<TOptions>> validations) { _setups = setups; _postConfigures = postConfigures; _validations = validations; } public TOptions Create(string name) { var options = new TOptions(); foreach (var setup in _setups) { if (setup is IConfigureNamedOptions<TOptions> namedSetup) { namedSetup.Configure(name, options); } else if (name == Options.DefaultName) { setup.Configure(options); } } foreach (var post in _postConfigures) { post.PostConfigure(name, options); } if (_validations != null) { var failures = new List<string>(); foreach (var validate in _validations) { var result = validate.Validate(name, options); if (result.Failed) { failures.AddRange(result.Failures); } } if (failures.Count > 0) { throw new OptionsValidationException(name, typeof(TOptions), failures); } } return options; } }

ASP.NET Core 选项模式源码学习Options IOptions（二）

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原文地址：https://www.cnblogs.com/yyfh/p/12032983.html