C# - 如何 xml 反序列化对象本身？

Question

public class Options
    {
        public FolderOption FolderOption { set; get; }

        public Options()
        {
            FolderOption = new FolderOption();
        }


        public void Save()
        {
            XmlSerializer serializer = new XmlSerializer(typeof(Options));
            TextWriter textWriter = new StreamWriter(@"C:\Options.xml");
            serializer.Serialize(textWriter, this);
            textWriter.Close();
        }

        public void Read()
        {
            XmlSerializer deserializer = new XmlSerializer(typeof(Options));
            TextReader textReader = new StreamReader(@"C:\Options.xml");
            //this = (Options)deserializer.Deserialize(textReader);
            textReader.Close();

        }
    }
}

我成功地保存了，FolderOption 的所有成员都被反序列化了。但问题是如何读回来？该行 - //this = (Options)deserializer.Deserialize(textReader);不会工作。

编辑：这个问题有什么解决办法吗？我们可以在不分配这个的情况下达到同样的目的吗？那就是将选项对象反序列化回选项。我懒得按属性做。在最高级别上执行将节省大量精力。

Answer 1

将您的 .Read() 方法构建为返回读取对象的静态函数：

public static Options Read(string path)
{
    XmlSerializer deserializer = new XmlSerializer(typeof(Options));
    using (TextReader textReader = new StreamReader(path))
    {
        return (Options)deserializer.Deserialize(textReader);
    }
}

然后更改您的调用代码，而不是这样：

Options myOptions = new Options();
myOptions.Read(@"C:\Options.xml");

你做这样的事情：

Options myOptions = Options.Read(@"C:\Options.xml");

很好的区别在于，不可能有一个没有一些数据的 Options 对象。

Answer 2

如果您的 Options 类型是结构，这将起作用，因为您可以更改结构本身。

如果 Options 是一个类（引用类型），则不能将其分配给该实例中的引用类型的当前实例。建议您编写一个辅助类，并将您的 Read 和 Save 方法放在那里，像这样

     public class XmlSerializerHelper<T>
    {
        public Type _type;

        public XmlSerializerHelper()
        {
            _type = typeof(T);
        }


        public void Save(string path, object obj)
        {
            using (TextWriter textWriter = new StreamWriter(path))
            {
                XmlSerializer serializer = new XmlSerializer(_type);
                serializer.Serialize(textWriter, obj);
            }

        }

        public T Read(string path)
        {
            T result;
            using (TextReader textReader = new StreamReader(path))
            {
                XmlSerializer deserializer = new XmlSerializer(_type);
                result = (T)deserializer.Deserialize(textReader);
            }
            return result;

        }
    }

然后从调用者那里使用它来读取和保存对象，而不是从类中尝试它。

//In the caller

var helper=new XmlSerializerHelper<Options>();
var obj=new Options();

//Write and read
helper.Save("yourpath",obj);
obj=helper.Read("yourpath");

并将 XmlSerializerHelper 放在 Util 的命名空间中，它是可重用的，并且适用于任何类型。

Answer 3

根据定义，对象不能反序列化自身：它已经存在，反序列化会创建该类型的新实例。

有时创建一个新的空类实例，然后用从 XML 引入的信息填充它是有意义的。该实例也可能“几乎为空”。例如，您可能会这样做，以加载用户首选项，或者一般而言，将实例设置回它以前的方式。实例的“空”或“接近空”状态将是类的有效状态：它只是不知道它在被持久化之前曾经处于什么状态。

---

另外，我建议你养成实现“使用”块的习惯：

public void Save()
{
    XmlSerializer serializer = new XmlSerializer(typeof(Options));
    using (TextWriter textWriter = new StreamWriter(@"C:\Options.xml"))
    {
        serializer.Serialize(textWriter, this);
        // no longer needed: textWriter.Close();
    }
}

public void Read()
{
    XmlSerializer deserializer = new XmlSerializer(typeof(Options));
    using (TextReader textReader = new StreamReader(@"C:\Options.xml"))
    {
        // no longer needed: textReader.Close();
    }
}

这将确保 TextReader 被处理掉，即使抛出异常也是如此。这就是不再需要关闭调用的原因。

Answer 4

我认为序列化和反序列化对象的最简单方法是使用具有以下两种方法的静态类。我们还需要一个名为 StringWriterWithEncoding 的类来设置 XML 字符串的 Encoding，因为标准 StringWriter 类的 Encoding 属性是只读的。 （在这里找到：http://devproj20.blogspot.com/2008/02/writing-xml-with-utf-8-encoding-using.html）

public static class GenericXmlSerializer
{
    public static string Serialize<T>(T obj, Encoding encoding)
    {
        XmlSerializer serializer = new XmlSerializer(typeof(T));            
        TextWriter textWriter = new StringWriterWithEncoding(new StringBuilder(), encoding);
        serializer.Serialize(textWriter, obj);

        return textWriter.ToString();
    }

    public static T Deserialize<T>(string xml)
    {
        XmlSerializer serializer = new XmlSerializer(typeof(T));
        TextReader textReader = new StringReader(xml);
        return (T)serializer.Deserialize(textReader);
    }
}

public class StringWriterWithEncoding : StringWriter
{
    Encoding encoding;

    public StringWriterWithEncoding(StringBuilder builder, Encoding encoding)
        : base(builder)
    {
        this.encoding = encoding;
    }

    public override Encoding Encoding
    {
        get { return encoding; }
    }
}

用法：

//serialize
MyClass myClass = new MyClass();
string xml = GenericXmlSerializer.Serialize<MyClass>(myClass, Encoding.Unicode);

//deserialize
MyClass myClass2 = GenericXmlSerializer.Deserialize<MyClass>(xml);

Answer 5

我是扩展方法的粉丝，因此我总是使用它：

using System.IO;
using System.Xml.Serialization;

public static class SerializationExtensionMethods
{
    /// <summary>
    /// Serializes the object.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="toSerialize">To serialize.</param>
    /// <returns></returns>
    public static string SerializeObjectToXml<T>(this T toSerialize)
    {
        XmlSerializer xmlSerializer = new XmlSerializer(toSerialize.GetType());
        StringWriter textWriter = new StringWriter();

        xmlSerializer.Serialize(textWriter, toSerialize);
        return textWriter.ToString();
    }

    /// <summary>
    /// Serializes the object.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="toSerialize">To serialize.</param>
    /// <param name="path">The path.</param>
    public static void SerializeObjectToFile<T>(this T toSerialize, string path)
    {
        string xml = SerializeObjectToXml<T>(toSerialize);

        using (StreamWriter sw = new StreamWriter(path, false))
        {
            sw.Write(xml);
        }
    }

    /// <summary>
    /// Deserializes the specified XML.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="xml">The XML.</param>
    /// <returns></returns>
    public static T DeserializeFromXml<T>(this T original, string xml)
    {
        XmlSerializer serializer = new XmlSerializer(typeof(T));
        TextReader textReader = new StringReader(xml);
        return (T)serializer.Deserialize(textReader);
    }

    /// <summary>
    /// Deserializes the specified object.
    /// </summary>
    /// <typeparam name="T"></typeparam>
    /// <param name="original">The original.</param>
    /// <param name="path">The path.</param>
    /// <returns></returns>
    public static T DeserializeFromFile<T>(this T original, string path)
    {
        string xml = string.Empty;

        using (StreamReader sr = new StreamReader(path))
        {
            xml = sr.ReadToEnd();
        }

        return DeserializeFromXml<T>(original, xml);
    }
}

用于序列化：

YourClassType obj = new YourClassType();

或

List<YourClassType> obj = new List<YourClassType>();

string xml = obj.SerializeObjectToXml();

或

obj.SerializeObjectToFile("PathToYourFile"); // It will save a file with your classes serialized (works with everything with the [Serializable] attribute).

用于反序列化：

YourClassType obj = new YourClassType().DeserializeFromXml("XML string here");
List<YourClassType> obj = new List<YourClassType>().DeserializeFromFile("XML string here");

或

YourClassType obj = new YourClassType().DeserializeFromFile("PathToYourFile");

你让它运行了:)

我更喜欢扩展方法，因为它可以让你的代码非常干净，这适用于你拥有的每一种对象类型，只要它实现了 [Serializable] 属性。

如果您需要指定序列化的方式（作为节点或属性），您可以在每个属性上添加属性，例如：

[XmlElement("NameOfTheElementYouWant")] 
[XmlAttribute("NameOfTheAttributeYouWant")]
[XmlText]

希望这对将来的某人有所帮助。

亚历杭德罗

Answer 6

我选择了这种方法（在 vb 中）

    Public Class SerialisableClass

    Public Sub SaveToXML(ByVal outputFilename As String)

        Dim xmls = New System.Xml.Serialization.XmlSerializer(Me.GetType)
        Using sw = New IO.StreamWriter(outputFilename)
            xmls.Serialize(sw, Me)
        End Using

    End Sub

    Private tempState As Object = Me
    Public Sub ReadFromXML(ByVal inputFilename As String)

        Dim xmls = New System.Xml.Serialization.XmlSerializer(Me.GetType)

        Using sr As New IO.StreamReader(inputFilename)
            tempState = xmls.Deserialize(sr)
        End Using

        For Each pi In tempState.GetType.GetProperties()

            Dim name = pi.Name

            Dim realProp = (From p In Me.GetType.GetProperties
                            Where p.Name = name And p.MemberType = Reflection.MemberTypes.Property).Take(1)(0)

            realProp.SetValue(Me, pi.GetValue(tempState, Nothing), Nothing)

        Next

    End Sub

End Class

然后我可以简单地使用这样的东西：

Public Class ClientSettings

    Inherits SerialisableClass

    Public Property ZipExePath As String
    Public Property DownloadPath As String
    Public Property UpdateInstallPath As String

End Class

然后这样称呼它：

Dim cs As New ClientSettings
cs.ReadFromXML("c:\myXMLfile.xml")

甚至更好（如果我添加必要的构造函数）：

Dim cs as New ClientSettings("c:\myXMLFile.xml")

对我来说它看起来很干净，并且在我的情况下效果很好。

干杯

Answer 7

参见XmlSerializer.Deserialize Method：您可以创建如下静态方法：

    public static Options DeserializeFromFile(string filename) {    
       // Create an instance of the XmlSerializer specifying type and namespace.
       XmlSerializer serializer = new XmlSerializer(typeof(Options));

       // A FileStream is needed to read the XML document.
       using (FileStream fs = new FileStream(filename, FileMode.Open)) {
           XmlReader reader = new XmlTextReader(fs);
           return (Options) serializer.Deserialize(reader);
       } // using
    }

上面可以这样称呼：

 Options foo = Options.DeserializeFromFile(@"C:\Options.xml");