如何修复：避免使用非只读静态字段

Question

我正在使用 NDepend，在下面的代码中，它检测到这种代码味道。

但是如果我添加只读，那么它就不会编译。

namespace todo
{
    using System;
    using System.Collections.Generic;
    using System.Configuration;
    using System.Linq;
    using System.Linq.Expressions;
    using System.Threading.Tasks;
    using Microsoft.Azure.Documents;
    using Microsoft.Azure.Documents.Client;
    using Microsoft.Azure.Documents.Linq;

    public static class DocumentDBRepository<T> where T : class
    {
        private static readonly string DatabaseId = ConfigurationManager.AppSettings["database"];
        private static readonly string CollectionId = ConfigurationManager.AppSettings["collection"];
        private static DocumentClient client;

        public static async Task<T> GetItemAsync(string id)
        {
            try
            {
                Document document = await client.ReadDocumentAsync(UriFactory.CreateDocumentUri(DatabaseId, CollectionId, id));
                return (T)(dynamic)document;
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    return null;
                }
                else
                {
                    throw;
                }
            }
        }

        public static async Task<IEnumerable<T>> GetItemsAsync(Expression<Func<T, bool>> predicate)
        {
            IDocumentQuery<T> query = client.CreateDocumentQuery<T>(
                UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId),
                new FeedOptions { MaxItemCount = -1 })
                .Where(predicate)
                .AsDocumentQuery();

            List<T> results = new List<T>();
            while (query.HasMoreResults)
            {
                results.AddRange(await query.ExecuteNextAsync<T>());
            }

            return results;
        }

        public static async Task<Document> CreateItemAsync(T item)
        {
            return await client.CreateDocumentAsync(UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId), item);
        }

        public static async Task<Document> UpdateItemAsync(string id, T item)
        {
            return await client.ReplaceDocumentAsync(UriFactory.CreateDocumentUri(DatabaseId, CollectionId, id), item);
        }

        public static async Task DeleteItemAsync(string id)
        {
            await client.DeleteDocumentAsync(UriFactory.CreateDocumentUri(DatabaseId, CollectionId, id));
        }

        public static void Initialize()
        {
            client = new DocumentClient(new Uri(ConfigurationManager.AppSettings["endpoint"]), ConfigurationManager.AppSettings["authKey"]);
            CreateDatabaseIfNotExistsAsync().Wait();
            CreateCollectionIfNotExistsAsync().Wait();
        }

        private static async Task CreateDatabaseIfNotExistsAsync()
        {
            try
            {
                await client.ReadDatabaseAsync(UriFactory.CreateDatabaseUri(DatabaseId));
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    await client.CreateDatabaseAsync(new Database { Id = DatabaseId });
                }
                else
                {
                    throw;
                }
            }
        }

        private static async Task CreateCollectionIfNotExistsAsync()
        {
            try
            {
                await client.ReadDocumentCollectionAsync(UriFactory.CreateDocumentCollectionUri(DatabaseId, CollectionId));
            }
            catch (DocumentClientException e)
            {
                if (e.StatusCode == System.Net.HttpStatusCode.NotFound)
                {
                    await client.CreateDocumentCollectionAsync(
                        UriFactory.CreateDatabaseUri(DatabaseId),
                        new DocumentCollection { Id = CollectionId },
                        new RequestOptions { OfferThroughput = 1000 });
                }
                else
                {
                    throw;
                }
            }
        }
    }
}

警告线是：

private static DocumentClient client;

您建议如何修复此 NDepend 警告？

规则说明：

此规则对未声明为只读的静态字段发出警告。

在面向对象编程中，保存可修改状态的自然产物是实例字段。此类可变静态字段会在运行时造成对预期状态的混淆，并削弱代码的可测试性，因为每次测试都会重复使用相同的可变状态。

可以在此处找到有关该主题的更多讨论：http://codebetter.com/patricksmacchia/2011/05/04/back-to-basics-usage-of-static-members/

Answer 1

尝试将初始化移动到声明中：

private static readonly DocumentClient client = new DocumentClient( . . . . );

如何修复：避免使用非只读静态字段

How to fix: Avoid non-readonly static fields

c#

code-analysis

static-analysis

ndepend

static-code-analysis