編寫高質量代碼改善C#程序的157個建議——建議57：實現ISerializable的子類型應負責父類的序列化

2019-11-14 14:06:09

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建議57：實現ISerializable的子類型應負責父類的序列化

我們將要實現的繼承自ISerializable的類型Employee有一個父類Person，假設Person沒有實現序列化，而現在子類Employee卻需要滿足序列化的場景。不過序列化器并沒有默認處理Person類型對象，這些事情只能由我們自己做。

以下是一個不妥的實現，序列化器只發現和處理了Employee中Salary字段：

    class PRogram    {        static void Main()        {            Employee  liming = new Employee() { Name = "liming", Salary = 2000 };            BinarySerializer.SerializeToFile(liming, @"c:/", "person.txt");            Employee limingCopy = BinarySerializer.DeserializeFromFile<Employee>(@"c:/person.txt");            Console.WriteLine(string.Format("姓名：{0}", limingCopy.Name));            Console.WriteLine(string.Format("薪水：{0}", limingCopy.Salary));        }    }        public class Person    {        public string Name { get; set; }    }    [Serializable]    public class Employee : Person, ISerializable    {        public int Salary { get; set; }        public Employee()        {        }        protected Employee(SerializationInfo info, StreamingContext context)        {            Salary = info.GetInt32("Salary");        }        public override void GetObjectData(SerializationInfo info, StreamingContext context)        {            info.AddValue("Salary", Salary);        }    }

序列化工具類：

    public class BinarySerializer    {        //將類型序列化為字符串        public static string Serialize<T>(T t)        {            using (MemoryStream stream = new MemoryStream())            {                BinaryFormatter formatter = new BinaryFormatter();                formatter.Serialize(stream, t);                return System.Text.Encoding.UTF8.GetString(stream.ToArray());            }        }        //將類型序列化為文件        public static void SerializeToFile<T>(T t, string path, string fullName)        {            if (!Directory.Exists(path))            {                Directory.CreateDirectory(path);            }            string fullPath = Path.Combine(path, fullName);            using (FileStream stream = new FileStream(fullPath, FileMode.OpenOrCreate))            {                BinaryFormatter formatter = new BinaryFormatter();                formatter.Serialize(stream, t);                stream.Flush();            }        }        //將字符串反序列化為類型        public static TResult Deserialize<TResult>(string s) where TResult : class        {            byte[] bs = System.Text.Encoding.UTF8.GetBytes(s);            using (MemoryStream stream = new MemoryStream(bs))            {                BinaryFormatter formatter = new BinaryFormatter();                return formatter.Deserialize(stream) as TResult;            }        }        //將文件反序列化為類型        public static TResult DeserializeFromFile<TResult>(string path) where TResult : class        {            using (FileStream stream = new FileStream(path, FileMode.Open))            {                BinaryFormatter formatter = new BinaryFormatter();                return formatter.Deserialize(stream) as TResult;            }        }    }

View Code

輸出為：

姓名：
薪水：2000

看見，Name字段并沒有正確處理。這需要我們修改類型Employee中受保護的構造方法GetObjectData方法，為它加入父類字段的處理：

    [Serializable]    public class Employee : Person, ISerializable    {        public int Salary { get; set; }        public Employee()        {        }        protected Employee(SerializationInfo info, StreamingContext context)        {            Name = info.GetString("Name");            Salary = info.GetInt32("Salary");        }        public void GetObjectData(SerializationInfo info, StreamingContext context)        {            info.AddValue("Name", Name);            info.AddValue("Salary", Salary);        }    }

修改后輸出：

姓名：liming
薪水：2000

上面的例子中Person類未被設置成支持序列化。現在，假設Person類已經實現了ISerializable接口，那么這個問題處理起來會相對容易，在子類Employee中，我們只需要調用父類受保護的構造方法和GetObjectData方法就可以了。如下所示：

    [Serializable]    public class Person : ISerializable    {        public string Name { get; set; }        public Person()        {        }        protected Person(SerializationInfo info, StreamingContext context)        {            Name = info.GetString("Name");        }        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)        {            info.AddValue("Name", Name);        }    }    [Serializable]    public class Employee : Person, ISerializable    {        public int Salary { get; set; }        public Employee()        {        }        protected Employee(SerializationInfo info, StreamingContext context)            : base(info, context)        {            Salary = info.GetInt32("Salary");        }        public override void GetObjectData(SerializationInfo info, StreamingContext context)        {            base.GetObjectData(info, context);            info.AddValue("Salary", Salary);        }    }