避免非只读静态字段-不变性NDepend

Question

我正在使用NDepend进行代码分析，并收到以下警告：

https://www.ndepend.com/default-rules/NDepend-Rules-Explorer.html?ruleid=ND1901#！

此规则警告未声明为只读的静态字段。

在面向对象编程中，实例字段是用于保存可修改状态的自然工件。这种可变的静态字段会在运行时引起对预期状态的混淆，并损害代码的可测试性，因为对于每个测试都重复使用相同的可变状态。

我的代码如下：

using Cosmonaut;
using Microsoft.Azure.Documents.Client;
using System.Configuration;
using LuloWebApi.Entities;


namespace LuloWebApi.Components
{
    /// <summary>
    /// Main class that encapsulates the creation of instances to connecto to Cosmos DB
    /// </summary>
    public sealed class CosmosStoreHolder
    {
        /// <summary>
        /// Property to be initiated only once in the constructor (singleton)
        /// </summary>
        private static CosmosStoreHolder instance = null;

        /// <summary>
        /// To block multiple instance creation
        /// </summary>
        private static readonly object padlock = new object();

        /// <summary>
        /// CosmosStore object  to get tenants information
        /// </summary>
        public Cosmonaut.ICosmosStore<SharepointTenant> CosmosStoreTenant { get; }

        /// <summary>
        /// CosmosStore object  to get site collection information
        /// </summary>
        public Cosmonaut.ICosmosStore<SiteCollection> CosmosStoreSiteCollection { get; }

        /// <summary>
        /// CosmosStore object  to get page templates information
        /// </summary>
        public Cosmonaut.ICosmosStore<PageTemplate> CosmosStorePageTemplate { get; }

        /// <summary>
        /// CosmosStore object  to get pages information
        /// </summary>
        public Cosmonaut.ICosmosStore<Page> CosmosStorePage { get; }

        /// <summary>
        /// CosmosStore object  to get roles information
        /// </summary>
        public Cosmonaut.ICosmosStore<Role> CosmosStoreRole { get; }

        /// <summary>
        /// CosmosStore object  to get clients information
        /// </summary>
        public Cosmonaut.ICosmosStore<Client> CosmosStoreClient { get; }

        /// <summary>
        /// CosmosStore object  to get users information
        /// </summary>
        public Cosmonaut.ICosmosStore<User> CosmosStoreUser { get; }

        /// <summary>
        /// CosmosStore object  to get partners information
        /// </summary>
        public Cosmonaut.ICosmosStore<Partner> CosmosStorePartner { get; }

        /// <summary>
        /// CosmosStore object  to get super administrators information
        /// </summary>
        public Cosmonaut.ICosmosStore<SuperAdministrator> CosmosStoreSuperAdministrator { get; }

        /// <summary>
        /// Constructor
        /// </summary>
        CosmosStoreHolder()
        {

            CosmosStoreSettings settings = new Cosmonaut.CosmosStoreSettings(ConfigurationManager.AppSettings["database"].ToString(),
                 ConfigurationManager.AppSettings["endpoint"].ToString(),
                 ConfigurationManager.AppSettings["authKey"].ToString());

            settings.ConnectionPolicy = new ConnectionPolicy
            {
                ConnectionMode = ConnectionMode.Direct,
                ConnectionProtocol = Protocol.Tcp
            };


            CosmosStoreTenant = new CosmosStore<SharepointTenant>(settings);
            CosmosStoreSiteCollection = new CosmosStore<SiteCollection>(settings);
            CosmosStorePageTemplate = new CosmosStore<PageTemplate>(settings);
            CosmosStorePage = new CosmosStore<Page>(settings);
            CosmosStoreRole = new CosmosStore<Role>(settings);
            CosmosStoreClient = new CosmosStore<Client>(settings);
            CosmosStoreUser = new CosmosStore<User>(settings);
            CosmosStorePartner = new CosmosStore<Partner>(settings);
            CosmosStoreSuperAdministrator = new CosmosStore<SuperAdministrator>(settings);
        }

        /// <summary>
        /// Instance access, singleton
        /// </summary>
        public static CosmosStoreHolder Instance
        {
            get
            {
                lock (padlock)
                {
                    if (instance == null)
                    {
                        instance = new CosmosStoreHolder();
                    }
                    return instance;
                }
            }
        }
    }
}

但是，我不确定如何解决此警告。

Answer 1

这是一个指导，而不是硬性规定。通常，非只读静态字段很难理解。但是在这种情况下，您正在执行延迟延迟加载，因此... a lock和mutate确实是实现此目的的一种方法，而不会导致过早加载。

因此，务实的解决方案是：忽略/覆盖警告

另一种方法，然而，是到外地迁移到另一种类型的它是只读的，并依靠递延.cctor语义：

public static CosmosStoreHolder Instance {
   [MethodImpl(MethodImplOptions.NoInlining)]
   get => DeferredHolder.Instance;
}

private static class DeferredHolder {
    internal static readonly CosmosStoreHolder Instance = new CosmosStoreHolder();
}

然后，您甚至不需要锁语义（.cctor为您处理）。