如何在重命名某些属性后反序列化旧 XML 文件？

Question

为简单起见，假设我有这个 class:

public class Person
{
    public int Id { get; set; }
    public string Name { get; set; }
}

我使用以下两种方法 serialization/deserialization:

public void Serialize(Person person, string outputFilePath)
{
    using (var stream = 
           new FileStream(outputFilePath, FileMode.Create, FileAccess.Write))
    {
        var serializer = new XmlSerializer(person.GetType());
        serializer.Serialize(stream, person);
    }
}

public Person Deserialize(string filePath)
{
    using (var stream = new FileStream(filePath, FileMode.Open))
    {
        var serializer = new XmlSerializer(typeof(Person));
        return (Person)serializer.Deserialize(stream);
    }
}

现在，假设我将一些 Person 对象序列化为 XML 文件，然后重命名 Person class 中的一个或多个属性：

// Renamed from `Name`
public string FullName { get; set; }

我的目标是允许程序仍然反序列化那些具有 Name 元素的旧 XML 文件，而不是 FullName

XmlElementAttribute 在这里无济于事：

// If I do this, I can't deserialize from files created after
// the property has been renamed.
[XmlElement("Name")]
public string FullName { get; set; }

如果我可以支持多个旧名称，也许使用一些属性，那将是理想的。例如，

[XmlAlternateDeserializationElement("Name")]
[XmlAlternateDeserializationElement("Label")]
public string FullName { get; set; }

但任何其他方式就足够了。我怎样才能做到这一点？

Answer 1

下面显示了如何在一个或多个属性名称发生更改时反序列化一个 XML 文件名。

注意：在下面的代码中，当XML被序列化时，它将以较新的格式保存。

XML - 原创

<Person>
    <Id>1</Id>
    <Name>John Smith</Name>
    <City>Some City</City>
</Person>

XmlPersonOriginal:

using System.Xml.Serialization;

namespace XmlSerializationRenamedProperty
{
    [XmlRoot(ElementName = "Person", IsNullable = false)]
    public class XmlPersonOriginal
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string City { get; set; }
        public string StateOrProvince { get; set; }
    }
}

序列化

public static void SerializeObjectToXMLFile(object obj, string xmlFilename)
{
    using (System.IO.TextWriter xmlStream = new System.IO.StreamWriter(xmlFilename))
    {
        System.Xml.Serialization.XmlSerializerNamespaces ns = new System.Xml.Serialization.XmlSerializerNamespaces();
        ns.Add(string.Empty, "urn:none");

        //create new instance
        System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(obj.GetType());

        //write to XML file
        serializer.Serialize(xmlStream, obj, ns);
    }
}

用法（序列化）：

string filename = @"C:\Temp\Person.xml";
XmlPersonOriginal person = new XmlPersonOriginal() { Id = 1, Name = "John Smith", City = "Some City"};
Helper.SerializeObjectToXMLFile(person, filename);

反序列化

public static T DeserializeXMLFileToObject<T>(string xmlFilename)
{
    T rObject = default(T);

    using (System.IO.StreamReader xmlStream = new System.IO.StreamReader(xmlFilename))
    {
        System.Xml.Serialization.XmlSerializer serializer = new System.Xml.Serialization.XmlSerializer(typeof(T));
        rObject = (T)serializer.Deserialize(xmlStream);
    }

    return rObject;
}

用法（反序列化）：

string filename = @"C:\Temp\Person.xml";
XmlPersonOriginal person = Helper.DeserializeXMLFileToObject<XmlPersonOriginal>(filename);

现在，如果决定将属性名称从 Name 更改为 FullName，则可以创建一个新的 class (XmlPerson_v2)继承自原始 (XmlPersonOriginal) 并覆盖任何已更改的属性名称。为了能够覆盖属性，将关键字“virtual”添加到属性.

XmlPersonOriginal:

using System.Xml.Serialization;

namespace XmlSerializationRenamedProperty
{
    [XmlRoot(ElementName = "Person", IsNullable = false)]
    public class XmlPersonOriginal
    {
        public int Id { get; set; }
        public virtual string Name { get; set; }
        public string City { get; set; }
        public string StateOrProvince { get; set; }
    }
}

XmlPerson_v2:

using System;
using System.Xml.Serialization;

namespace XmlSerializationRenamedProperty
{
    [XmlRoot(ElementName = "Person", IsNullable = false)]
    public class XmlPerson_v2 : XmlPersonOriginal
    {
        public string FullName { get; set; }

        #pragma warning disable CS0809
        [XmlIgnore]
        [Obsolete("Name is deprecated, use FullName instead.")]
        public override string Name 
        {
            get
            {
                return base.Name;
            }

            set
            {
                FullName = value;
            }
        }
    }
}

用法（序列化）：

string filename = @"C:\Temp\PersonModified.xml";
XmlPerson_v2 person = new XmlPerson_v2() { Id = 1, FullName = "John Smith", City = "Some City"};
Helper.SerializeObjectToXMLFile(person, filename);

用法（反序列化）：

string filename = @"C:\Temp\Person.xml";
XmlPerson_v2 person = Helper.DeserializeXMLFileToObject<XmlPerson_v2>(filename);

用法（反序列化）：

string filename = @"C:\Temp\PersonModified.xml";
XmlPerson_v2 person = Helper.DeserializeXMLFileToObject<XmlPerson_v2>(filename);

资源

How to mark a method as obsolete or deprecated?
ObsoleteAttribute Class
Suppress code analysis violations

Answer 2

您可以利用 XmlSerializer 的 UnknownElement / UnknownAttribute 事件来处理旧的元素名称或属性名称：

var serializer = new XmlSerializer(typeof(Person));
serializer.UnknownElement += (sender, e) =>
{
   var person = (Person)e.ObjectBeingDeserialized;
   if (e.Element.Name == "Name")
   {
       person.FullName = e.Element.InnerText;
   }
};

这可以保持您的实际数据类干净并将兼容性代码集中在序列化方法中。

如何在重命名某些属性后反序列化旧 XML 文件？

How to deserialize old XML files after some properties have been renamed?

.net

c#

xml-serialization