一. 咱們的需求

你是否和我同樣有以下的困擾：程序員

你須要將一個類轉換爲XML或JSON存儲或傳輸，但總有你不想存儲或想特殊處理的字段，用序列化器自身的反射功能就看起來頗爲雞肋了。
與MongoDB等鍵值對數據庫作交互，不少ORM框架都無效了，如何寫一個通用的數據接口層？並且不用去添加醜陋的"MongoIgnore"這樣的attribute?
你要將一個對象的屬性「拷貝」到另一個對象，怎麼作？C語言的拷貝構造函數？那太原始了。
界面綁定：總有一些綁定表達式，想經過動態的形式提交給框架，而不是寫死在xaml裏，那是否又得在C#裏寫一堆對象映射的代碼了？

你們確定都遇到過和我類似的困擾，爲了存儲或讀取某個對象（好比從文件或數據庫裏讀取），你不得不寫下大量數據類型轉換和賦值語句，並且在程序中不能複用，這樣的代碼處處都是，真是代碼的臭味。數據庫

因爲鍵值對的概念已經深刻人心，因而便有了這樣一個叫作「字典序列化」的接口，該接口不是官方定義的，而是我根據實際需求總結的，同時我發現，它真的很是好用。數組

廢話不說，先看該接口的定義：框架

  /// <summary>
    /// 進行字典序列化的接口，方便實現鍵值對的映射關係和重建
    /// </summary>
    public interface IDictionarySerializable
    {
        /// <summary>
        /// 從數據到字典
        /// </summary>
        /// <returns></returns>
        IDictionary<string, object> DictSerialize(Scenario scenario = Scenario.Database);

        /// <summary>
        /// 從字典到數據
        /// </summary>
        /// <param name="dicts">字典</param>
        /// <param name="scenario">應用場景</param>
        void DictDeserialize(IDictionary<string, object> dicts, Scenario scenario = Scenario.Database);
    }

它只有兩個方法，一個是從字典中讀取數據到實體類，另外一個是將實體類的數據寫入字典。你要作的，就是讓你的實體類實現這個接口。ide

值得注意的是，函數參數中有一個Scenario枚舉，該枚舉指定了轉換的場景，例如數據庫和用戶界面，在轉換時可能就有必定的區別，程序員可經過實際狀況來肯定，具體緣由能夠看下邊的部分。你能夠傳入更多的參數，指示該接口的獨特序列化方法。函數

二. 如何使用？

先定義一個實體類：Artical, 它是一個簡單的POCO類型，包含Title等六個屬性，爲了節約篇幅，就不在此聲明它了。咱們先看以下的代碼：性能

  //define a entity named Artical with following propertynames
   public void DictDeserialize(IDictionary<string, object> dicts)
        {
            Title = (string)dicts["Title"];
            PublishTime = (DateTime)dicts["PublishTime"];
            Author = (string)dicts["Author"];
            ArticalContent = (string)dicts["ArticalContent"];
            PaperID =  (int)dicts["PaperID"];
            ClassID =  (string)dicts["ClassID"];
        }
     public IDictionary<string, object> DictSerialize()
        {
            var dict = new Dictionary<string, object>
                {
                    { "Title", this.Title },
                    { "PublishTime", this.PublishTime.Value },
                    { "Author", this.Author },
                    { "ArticalContent", this.ArticalContent },
                    { "PaperID", this.PaperID.Value },
                    { "ClassID", this.ClassID }
                };
            return dict;
        }

它指示了最經常使用的使用場景。但是讀者可能會注意到如下問題：ui

Title = (string)dicts["Title"]; this

(1) 若是字典中沒有對應的屬性項，那麼經過索引器讀這個屬性是會報錯的。spa

(2) 即便有對應的屬性項，可它的值是Null，那麼它可能覆蓋掉本來是正常的屬性值。

(3) 類型不統一：這個字典多是由JSON序列化器提供的，或是由某數據庫的驅動提供的，那麼，一個表示時間的字段，傳過來的類型多是DateTime,也多是string，如何不用醜陋的代碼作複雜的判斷和轉換呢？

對此，咱們添加了一個IDictionary的擴展方法：

public static T Set<T>(this IDictionary<string, object> dict, string key, T oldValue)
        {
            object data = null;
            if (dict.TryGetValue(key, out data))
            {
                Type type = typeof(T);
                if (type.IsEnum)
                {
                    var index = (T)Convert.ChangeType(data, typeof(int));
                    return (index);
                }
                if (data == null)
                {
                    return oldValue;
                }
                var value = (T)Convert.ChangeType(data, typeof(T));
                return value;
            }

            return oldValue;
        }

因而，從字典中讀取數據（字典反序列化），就能夠變得像下面這樣優雅了，因爲編譯器的自動類型推斷功能，連T都不用寫了。若是數據獲取失敗，原有值不受影響。

 public void DictDeserialize(IDictionary<string, object> dicts, Scenario scenario = Scenario.Database)
        {
            this.Title = dicts.Set("Title", this.Title);
            this.PublishTime = dicts.Set("PublishTime", this.PublishTime);
            this.Author = dicts.Set("Author", this.Author);
            this.ArticalContent = dicts.Set("ArticalContent", this.ArticalContent);
            this.PaperID = dicts.Set("PaperID", this.PaperID);
            this.ClassID = dicts.Set("ClassID", this.ClassID);  
        }

但是，又會有人問，若是某屬性的類型是List<T>,好比是string的數組呢？

這個問題會有點複雜，如何保存一個List<string>呢？若是是MongoDB，它的驅動是能直接存儲/返回List<string>的，但若是是文件存儲，通常會存儲成JSON格式，例如["a","b","c","d"]這樣的格式，所以咱們能夠定義以下的擴展方法：

        public static List<T> SetArray<T>(this IDictionary<string, object> dict, string key, List<T> oldValue)
           
        {
            object data = null;

            if (dict.TryGetValue(key, out data))
            {
                var list = data as List<T>;
                if (list != null) return list;
                string str = data.ToString();
                if (str=="[]")
                    return oldValue;
                if (str[0] != '[') return oldValue;
                return JsonConvert.Import<List<T>>(str);
            }
            return oldValue.ToList();
        }

這裏爲了轉換JSON風格的string,用了第三方的JSON轉換庫：Jayrock.Json. 若是你本身有數組和string的轉換方法，不妨能夠寫新的擴展方法。

經過該接口，可方便的實現對象間的數據拷貝：

    public T Copy<T>(T oldValue) where T : IDictionarySerializable, new()
        {
            IDictionary<string, object> data = oldValue.DictSerialize();
            var newValue = new T();
            newValue.DictDeserialize(data);
            return newValue;
        }

三. 如何作數據庫接口層？

有了這樣的接口，咱們就能夠方便的作一個數據接口層，隔離數據庫和真實類型了，下面依舊以MongoDB爲例。若是咱們須要獲取表內全部的對象，可用以下的方法：

  /// <summary>
        /// 獲取數據庫中的全部實體
        /// </summary>
        /// <returns></returns>
        public List<T> GetAllEntitys<T>(string tableName) where T : IDictionarySerializable, new()
        {
            if (this.IsUseable == false)
            {
                return new List<T>();
            }

            IMongoCollection<Document> collection = this.DB.GetCollection<Document>(tableName);
            var documents = collection.FindAll().Documents.ToList();
            var list = new List<T>();
            foreach (Document document in documents)
            {
                var user = new T();
                user.DictDeserialize(document);
                list.Add(user);
            }
            return list;
        }

若是想更新或保存一個文檔，能夠用以下的代碼：

  /// <summary>
        /// 更新或增長一個新文檔
        /// </summary>
        /// <param name="entity"></param>
        /// <param name="tableName">表名 </param>
        /// <param name="keyName"> </param>
        /// <param name="keyvalue"> </param>
        public void SaveOrUpdateEntity(IDictionarySerializable entity, string tableName, string keyName, object keyvalue)
        {
            if (this.IsUseable == false)
            {
                return;
            }
            IMongoCollection<Document> collection = this.DB.GetCollection<Document>(tableName);
            Document document = collection.FindOne(new Document { { keyName, keyvalue } });
            if (document != null)
            {
                this.UpdateDocument(entity, document);
                collection.Save(document);
            }
            else
            {
                Document doc = this.GetNewDocument(entity);
                collection.Save(doc);
            }
        }

  
 private Document GetNewDocument(IDictionarySerializable entity)
        {
            IDictionary<string, object> datas = entity.DictSerialize();

            var document = new Document(datas);

            return document;
        }

        private void UpdateDocument(IDictionarySerializable data, Document document)
        {
            IDictionary<string, object> datas = data.DictSerialize();
            foreach (string key in datas.Keys)
            {
                document[key] = datas[key];
            }
        }

SaveOrUpdateCode

能夠經過泛型或者接口的方法，方便的讀取/存儲這些數據。

完整的驅動層代碼，在這裏：

  /// <summary>
    /// Mongo數據庫服務
    /// </summary>
    public class MongoServiceBase
    {
        #region Constants and Fields

        protected IMongoDatabase DB;

        protected Mongo Mongo;

        private Document update;

        #endregion

        //連接字符串 

        #region Properties

        public string ConnectionString { get; set; }

        //數據庫名 
        public string DBName { get; set; }

        public bool IsUseable { get; set; }

        /// <summary>
        /// 本地數據庫位置
        /// </summary>
        public string LocalDBLocation { get; set; }

        #endregion

        #region Public Methods

        /// <summary>
        /// 鏈接到數據庫，只需執行一次
        /// </summary>
        public virtual bool ConnectDB()
        {
            var config = new MongoConfigurationBuilder();

            config.ConnectionString(this.ConnectionString);
            //定義Mongo服務 

            this.Mongo = new Mongo(config.BuildConfiguration());

            if (this.Mongo.TryConnect())
            {
                this.IsUseable = true;
                this.update = new Document();

                this.update["$inc"] = new Document("id", 1);

                this.DB = this.Mongo.GetDatabase(this.DBName);
            }
            else
            {
                this.IsUseable = false;
            }
            return this.IsUseable;
        }

        public T Copy<T>(T oldValue) where T : IDictionarySerializable, new()
        {
            IDictionary<string, object> data = oldValue.DictSerialize();
            var newValue = new T();
            newValue.DictDeserialize(data);
            return newValue;
        }

        /// <summary>
        /// 建立一個自增主鍵索引表
        /// </summary>
        /// <param name="tableName">表名</param>
        public void CreateIndexTable(string tableName)
        {
            if (this.IsUseable == false)
            {
                return;
            }
            IMongoCollection idManager = this.DB.GetCollection("ids");
            Document idDoc = idManager.FindOne(new Document("Name", tableName));
            if (idDoc == null)
            {
                idDoc = new Document();
                idDoc["Name"] = tableName;
                idDoc["id"] = 0;
            }

            idManager.Save(idDoc);
        }

        /// <summary>
        /// 獲取數據庫中的全部實體
        /// </summary>
        /// <returns></returns>
        public List<T> GetAllEntitys<T>(string tableName) where T : IDictionarySerializable, new()
        {
            if (this.IsUseable == false)
            {
                return new List<T>();
            }

            IMongoCollection<Document> collection = this.DB.GetCollection<Document>(tableName);
            List<Document> documents = collection.FindAll().Documents.ToList();
            var list = new List<T>();
            foreach (Document document in documents)
            {
                var user = new T();
                user.DictDeserialize(document);
                list.Add(user);
            }
            return list;
        }

        /// <summary>
        /// 獲取必定範圍的實體
        /// </summary>
        /// <param name="tableName"></param>
        /// <param name="type"></param>
        /// <param name="mount"></param>
        /// <param name="skip"></param>
        /// <returns></returns>
        public List<IDictionarySerializable> GetAllEntitys(string tableName, Type type)
        {
            if (this.IsUseable == false)
            {
                return new List<IDictionarySerializable>();
            }

            List<Document> docuemts = this.DB.GetCollection<Document>(tableName).FindAll().Documents.ToList();
            var items = new List<IDictionarySerializable>();
            foreach (Document document in docuemts)
            {
                object data = Activator.CreateInstance(type);
                var suck = (IDictionarySerializable)data;
                suck.DictDeserialize(document);
                items.Add(suck);
            }
            return items;
        }

        /// <summary>
        /// 獲取必定範圍的實體
        /// </summary>
        /// <param name="tableName"></param>
        /// <param name="type"></param>
        /// <param name="mount"></param>
        /// <param name="skip"></param>
        /// <returns></returns>
        public List<IDictionarySerializable> GetEntitys(string tableName, Type type, int mount, int skip)
        {
            if (this.IsUseable == false)
            {
                return new List<IDictionarySerializable>();
            }

            List<Document> docuemts =
                this.DB.GetCollection<Document>(tableName).FindAll().Skip(skip).Limit(mount).Documents.ToList();
            var items = new List<IDictionarySerializable>();
            foreach (Document document in docuemts)
            {
                object data = Activator.CreateInstance(type);
                var suck = (IDictionarySerializable)data;
                suck.DictDeserialize(document);
                items.Add(suck);
            }
            return items;
        }

        public List<T> GetEntitys<T>(string tableName, int mount, int skip) where T : IDictionarySerializable, new()
        {
            if (this.IsUseable == false)
            {
                return new List<T>();
            }

            ICursor<Document> collection = this.DB.GetCollection<Document>(tableName).Find(null).Skip(skip).Limit(mount);

            var users = new List<T>();
            foreach (Document document in collection.Documents)
            {
                var user = new T();
                user.DictDeserialize(document);
                users.Add(user);
            }
            return users;
        }

        /// <summary>
        /// 直接插入一個實體
        /// </summary>
        /// <param name="user"></param>
        /// <param name="tableName"></param>
        public bool InsertEntity(IDictionarySerializable user, string tableName, string key, out int index)
        {
            if (this.IsUseable == false)
            {
                index = 0;
                return false;
            }

            IMongoCollection<Document> collection = this.DB.GetCollection<Document>(tableName);
            IMongoCollection idManager = this.DB.GetCollection("ids");
            Document docID = idManager.FindAndModify(this.update, new Document("Name", tableName), returnNew: true);

            //下面三句存入數據庫
            Document doc = this.GetNewDocument(user);

            doc[key] = docID["id"];
            index = (int)docID["id"];
            ;
            collection.Save(doc);
            return true;
        }

        public void RepairDatabase()
        {
            bool local = (this.ConnectionString.Contains("localhost") || this.ConnectionString.Contains("127.0.0.1"));
            if (local == false)
            {
                throw new Exception("MongoDB數據庫不在本地，沒法啓動自動數據庫修復");
            }

            var mydir = new DirectoryInfo(this.LocalDBLocation);
            FileInfo file = mydir.GetFiles().FirstOrDefault(d => d.Name == "mongod.lock");
            if (file == null)
            {
                throw new Exception("修復失敗，您是否沒有安裝MongoDB數據庫");
            }
            try
            {
                File.Delete(file.FullName);
                string str = CMDHelper.Execute("net start MongoDB");
            }
            catch (Exception ex)
            {
            }
        }

        /// <summary>
        /// 更新或增長一個新文檔
        /// </summary>
        /// <param name="entity"></param>
        /// <param name="tableName">表名 </param>
        /// <param name="keyName"> </param>
        /// <param name="keyvalue"> </param>
        public void SaveOrUpdateEntity(
            IDictionarySerializable entity, string tableName, string keyName, object keyvalue)
        {
            if (this.IsUseable == false)
            {
                return;
            }
            IMongoCollection<Document> collection = this.DB.GetCollection<Document>(tableName);
            Document document = collection.FindOne(new Document { { keyName, keyvalue } });
            if (document != null)
            {
                this.UpdateDocument(entity, document);
                collection.Save(document);
            }
            else
            {
                Document doc = this.GetNewDocument(entity);
                collection.Save(doc);
            }
        }

        public bool TryFindEntity<T>(string tableName, string keyName, object keyvalue, out T result)
            where T : class, IDictionarySerializable, new()
        {
            IMongoCollection<Document> collection = this.DB.GetCollection<Document>(tableName);
            Document document = collection.FindOne(new Document { { keyName, keyvalue } });
            if (document == null)
            {
                result = null;
                return false;
            }
            result = new T();
            try
            {
                result.DictDeserialize(document);
            }
            catch (Exception ex)
            {
                XLogSys.Print.Error(ex);
            }

            return true;
        }

        #endregion

        #region Methods

        private Document GetNewDocument(IDictionarySerializable entity)
        {
            IDictionary<string, object> datas = entity.DictSerialize();

            var document = new Document(datas);

            return document;
        }

        private void UpdateDocument(IDictionarySerializable data, Document document)
        {
            IDictionary<string, object> datas = data.DictSerialize();
            foreach (string key in datas.Keys)
            {
                document[key] = datas[key];
            }
        }

        #endregion
    }