如何将具有多态性的 c# 对象序列化为具有覆盖的肥皂属性的肥皂消息，类似于 XmlAttributeOverrides？

Question

我有一个动态创建的类型，所以我无法更改它的实现。我不能应用像

这样的解决方案

[SoapInclude()] 

想象一下，如果我有这样的课程：

public class BaseClass{}
public class DerivedClass:BaseClass{}
public class AnotherDerivedClass:BaseClass{}

public class RequestClass
{
    public BaseClass item{get;set;}
}

如果我们尝试简单地序列化，我们会得到 DerivedClass 未找到的异常，因此我们必须覆盖 xmlattributes。 我已经设法覆盖我的类型并使用XmlAttributeOverrides 对其进行序列化，如下所示：

var requestObject = new RequestClass() {item = new DerivedClass()};
XmlAttributes attrs = new XmlAttributes();
XmlElementAttribute attr = new XmlElementAttribute
{
    ElementName = "DerivedClass",
    Type = typeof(DerivedClass)
};
attrs.XmlElements.Add(attr);
XmlAttributeOverrides attoverrides = new XmlAttributeOverrides();
attoverrides.Add(typeof(RequestClass), "item", attrs);
XmlSerializer sr = new XmlSerializer(typeof(RequestClass), attoverrides);
StringWriter writer = new StringWriter();
sr.Serialize(writer, requestObject);
var xml = writer.ToString();

现在上面的工作，但我想要将我的对象序列化为肥皂消息。我找到了与上面类似的类，例如SoapAttributeOverrides，我试图用这些类覆盖它，但它似乎不起作用。我试过了：

var requestObject = new RequestClass(){item = new DerivedClass()};
SoapAttributeOverrides ovr = new SoapAttributeOverrides();
SoapAttributes soapAtts = new SoapAttributes();
SoapElementAttribute element = new SoapElementAttribute();
element.ElementName = "DerivedClass";
ovr.Add(typeof(RequestClass), "item", soapAtts);
var sr = new XmlSerializer(new SoapReflectionImporter(ovr).ImportTypeMapping(typeof(RequestClass)));
StringWriter writer = new StringWriter();
sr.Serialize(writer, requestObject);
var xml = writer.ToString();
writer.Close();

我再次收到异常未找到 DerivedClass。我怎样才能给SoapElementAttribute 一个类似于XmlElementAttribute.Type 的类型，以便可以通过覆盖进行序列化以支持BaseClass 的多态性？

Answer 1

.Net 中 SOAP 编码的 XML 序列化通过included type 机制支持多态性。为了在运行时将包含的类型添加到 SoapReflectionImporter，请使用：

• SoapReflectionImporter.IncludeType(Type)
• SoapReflectionImporter.IncludeTypes(ICustomAttributeProvider)。

因此，您可以按如下方式制造您的XmlSerializer：

public static XmlSerializer RequestClassSerializer { get; } 
    = CreateSoapSerializerWithBaseClassIncludedTypes(typeof(RequestClass), typeof(DerivedClass), typeof(AnotherDerivedClass));

static XmlSerializer CreateSoapSerializerWithBaseClassIncludedTypes(Type rootType, params Type [] includedTypes)
{
    var importer = new SoapReflectionImporter();
    foreach (var type in includedTypes)
        importer.IncludeType(type);
    return new XmlSerializer(importer.ImportTypeMapping(rootType));
}

然后介绍如下扩展方法：

public static partial class XmlSerializationHelper
{
    public static string GetSoapXml<T>(this T obj, XName wrapperName, XmlSerializer serializer = null)
    {
        using (var textWriter = new StringWriter())
        {
            var settings = new XmlWriterSettings() { Indent = true }; // For cosmetic purposes.
            using (var xmlWriter = XmlWriter.Create(textWriter, settings))
            {
                xmlWriter.WriteStartElement(wrapperName.LocalName, wrapperName.NamespaceName);
                (serializer ?? GetDefaultSoapSerializer(obj.GetType())).Serialize(xmlWriter, obj);
                xmlWriter.WriteEndElement();
            }
            return textWriter.ToString();
        }
    }

    static readonly Dictionary<Type, XmlSerializer> cache = new Dictionary<Type, XmlSerializer>();

    public static XmlSerializer GetDefaultSoapSerializer(Type type)
    {
        lock(cache)
        {
            if (cache.TryGetValue(type, out var serializer))
                return serializer;
            return cache[type] = new XmlSerializer(new SoapReflectionImporter().ImportTypeMapping(type));
        }
    }
}

您将能够按如下方式序列化您的requestObject：

var requestObject = new RequestClass(){item = new DerivedClass()};

var xml = requestObject.GetSoapXml("wrapper", RequestClassSerializer);

注意事项：

• 为避免严重的内存泄漏，您应该静态缓存任何不是使用XmlSerializer(Type) 或XmlSerializer(Type, String) 构造函数创建的XmlSerializer。原因请参见the documentation 和Memory Leak using StreamReader and XmlSerializer。

  如果您要动态生成类型系列，您可能需要将它们的序列化程序缓存在受lock 语句保护的静态字典中。

• 如 Extension method to serialize generic objects as a SOAP formatted stream 和 InvalidOperationException while SOAP serialization of complex type 中所述，您需要在使用 SOAP XML 序列化程序直接序列化为 XML 之前手动编写信封或其他包装元素。

  如果出于某种原因您只想将 SOAP XML 主体作为一系列 XML 片段，您可以这样做：

  public static string GetSoapBodyXml<T>(this T obj, XmlSerializer serializer = null)
  {
      using (var textWriter = new StringWriter())
      {
          var settings = new XmlWriterSettings() { Indent = true, ConformanceLevel = ConformanceLevel.Fragment }; // For cosmetic purposes.
          using (var xmlWriter = XmlWriter.Create(textWriter, settings))
          {
              xmlWriter.WriteWhitespace(""); // Hack to prevent an error about WriteStartDocument getting called for ConformanceLevel.Fragment
              (serializer ?? GetDefaultSoapSerializer(obj.GetType())).Serialize(xmlWriter, obj);
          }
          return textWriter.ToString();
      }
  }
  

演示小提琴here.