是否有一种普遍接受的方法来避免在 WCF 服务上使用 KnownType 属性？我一直在做一些研究，看起来有两种选择：
我不喜欢每次添加新类型时都必须静态添加 KnownType 属性，因此想要避免它。
是否应该使用第三种选择？如果是这样，它是什么？如果不是，那么以上两个选项中哪一个是正确的选择？
编辑 - 使用方法
第三种选择是使用反射
[DataContract]
[KnownType("DerivedTypes")]
public abstract class FooBase
{
private static Type[] DerivedTypes()
{
return typeof(FooBase).GetDerivedTypes(Assembly.GetExecutingAssembly()).ToArray();
}
}
我想发布迄今为止我能想到的最简单、最优雅的解决方案。如果出现另一个更好的答案，我会同意的。但就目前而言，这运作良好。
基类，只有一个 KnownType属性，指向一个名为的方法DerivedTypes()：
[KnownType("DerivedTypes")]
[DataContract]
public abstract class TaskBase : EntityBase
{
// other class members here
private static Type[] DerivedTypes()
{
return typeof(TaskBase).GetDerivedTypes(Assembly.GetExecutingAssembly()).ToArray();
}
}
该GetDerivedTypes()方法在一个单独的 ReflectionUtility 类中：
public static IEnumerable<Type> GetDerivedTypes(this Type baseType, Assembly assembly)
{
var types = from t in assembly.GetTypes()
where t.IsSubclassOf(baseType)
select t;
return types;
}
只要所有涉及的类都在同一个程序集中，Bob 提到的方法就可以工作。
以下方法将跨程序集工作：
[DataContract]
[KnownType("GetDerivedTypes")]
public class BaseClass
{
public static List<Type> DerivedTypes = new List<Type>();
private static IEnumerable<Type> GetDerivedTypes()
{
return DerivedTypes;
}
}
[DataContract]
public class DerivedClass : BaseClass
{
//static constructor
static DerivedClass()
{
BaseClass.DerivedTypes.Add(typeof(DerivedClass));
}
}
这是我对已接受答案的变体：
private static IEnumerable<Type> GetKnownTypes() {
Type baseType = typeof(MyBaseType);
return AppDomain.CurrentDomain.GetAssemblies()
.SelectMany(x => x.DefinedTypes)
.Where(x => x.IsClass && !x.IsAbstract && x.GetCustomAttribute<DataContractAttribute>() != null && baseType.IsAssignableFrom(x));
}
区别在于：
您可以在自定义类型中实现 IXmlSerializable 并手动处理其复杂性。您可以在下面找到示例代码：
[XmlRoot("ComplexTypeA")]
public class ComplexTypeA : IXmlSerializable
{
public int Value { get; set; }
public void WriteXml (XmlWriter writer)
{
writer.WriteAttributeString("Type", this.GetType().FullName);
writer.WriteValue(this.Value.ToString());
}
public void ReadXml (XmlReader reader)
{
reader.MoveToContent();
if (reader.HasAttributes) {
if (reader.GetAttribute("Type") == this.GetType().FullName) {
this.Value = int.Parse(reader.ReadString());
}
}
}
public XmlSchema GetSchema()
{
return(null);
}
}
[XmlRoot("ComplexTypeB")]
public class ComplexTypeB : IXmlSerializable
{
public string Value { get; set; }
public void WriteXml (XmlWriter writer)
{
writer.WriteAttributeString("Type", this.GetType().FullName);
writer.WriteValue(this.Value);
}
public void ReadXml (XmlReader reader)
{
reader.MoveToContent();
if (reader.HasAttributes) {
if (reader.GetAttribute("Type") == this.GetType().FullName) {
this.Value = reader.ReadString();
}
}
}
public XmlSchema GetSchema()
{
return(null);
}
}
[XmlRoot("ComplexTypeC")]
public class ComplexTypeC : IXmlSerializable
{
public Object ComplexObj { get; set; }
public void WriteXml (XmlWriter writer)
{
writer.WriteAttributeString("Type", this.GetType().FullName);
if (this.ComplexObj != null)
{
writer.WriteAttributeString("IsNull", "False");
writer.WriteAttributeString("SubType", this.ComplexObj.GetType().FullName);
if (this.ComplexObj is ComplexTypeA)
{
writer.WriteAttributeString("HasValue", "True");
XmlSerializer serializer = new XmlSerializer(typeof(ComplexTypeA));
serializer.Serialize(writer, this.ComplexObj as ComplexTypeA);
}
else if (tthis.ComplexObj is ComplexTypeB)
{
writer.WriteAttributeString("HasValue", "True");
XmlSerializer serializer = new XmlSerializer(typeof(ComplexTypeB));
serializer.Serialize(writer, this.ComplexObj as ComplexTypeB);
}
else
{
writer.WriteAttributeString("HasValue", "False");
}
}
else
{
writer.WriteAttributeString("IsNull", "True");
}
}
public void ReadXml (XmlReader reader)
{
reader.MoveToContent();
if (reader.HasAttributes) {
if (reader.GetAttribute("Type") == this.GetType().FullName) {
if ((reader.GetAttribute("IsNull") == "False") && (reader.GetAttribute("HasValue") == "True")) {
if (reader.GetAttribute("SubType") == typeof(ComplexTypeA).FullName)
{
XmlSerializer serializer = new XmlSerializer(typeof(ComplexTypeA));
this.ComplexObj = serializer.Deserialize(reader) as ComplexTypeA;
}
else if (reader.GetAttribute("SubType") == typeof(ComplexTypeB).FullName)
{
XmlSerializer serializer = new XmlSerializer(typeof(ComplexTypeB));
this.ComplexObj = serializer.Deserialize(reader) as ComplexTypeB;
}
}
}
}
}
public XmlSchema GetSchema()
{
return(null);
}
}
希望能帮助到你。
如果你不喜欢到处都有属性，那么你可以使用配置文件。
<system.runtime.serialization>
<dataContractSerializer>
<declaredTypes>
<add type = "Contact,Host,Version=1.0.0.0,Culture=neutral,
PublicKeyToken=null">
<knownType type = "Customer,MyClassLibrary,Version=1.0.0.0,
Culture=neutral,PublicKeyToken=null"/>
</add>
</declaredTypes>
</dataContractSerializer>
</system.runtime.serialization>
我宁愿一次性提取我的自定义类型并在序列化/反序列化期间使用它。读完这篇文章后，我花了一段时间才明白在哪里注入这个类型列表以对序列化器对象有用。答案很简单：这个列表将用作序列化器对象的构造函数的输入参数之一。
1-我使用两种静态通用方法进行序列化和反序列化，这可能或多或少是其他人也做这项工作的方式，或者至少与您的代码进行比较非常清楚：
public static byte[] Serialize<T>(T obj)
{
var serializer = new DataContractSerializer(typeof(T), MyGlobalObject.ResolveKnownTypes());
var stream = new MemoryStream();
using (var writer =
XmlDictionaryWriter.CreateBinaryWriter(stream))
{
serializer.WriteObject(writer, obj);
}
return stream.ToArray();
}
public static T Deserialize<T>(byte[] data)
{
var serializer = new DataContractSerializer(typeof(T), MyGlobalObject.ResolveKnownTypes());
using (var stream = new MemoryStream(data))
using (var reader =
XmlDictionaryReader.CreateBinaryReader(
stream, XmlDictionaryReaderQuotas.Max))
{
return (T)serializer.ReadObject(reader);
}
}
2- 请注意 DataContractSerializer 的构造函数。我们在那里有第二个参数，它是将已知类型注入序列化程序对象的入口点。
3- 我使用静态方法从我自己的程序集中提取我自己定义的所有类型。此静态方法的代码可能如下所示：
private static Type[] KnownTypes { get; set; }
public static Type[] ResolveKnownTypes()
{
if (MyGlobalObject.KnownTypes == null)
{
List<Type> t = new List<Type>();
List<AssemblyName> c = System.Reflection.Assembly.GetEntryAssembly().GetReferencedAssemblies().Where(b => b.Name == "DeveloperCode" | b.Name == "Library").ToList();
foreach (AssemblyName n in c)
{
System.Reflection.Assembly a = System.Reflection.Assembly.Load(n);
t.AddRange(a.GetTypes().ToList());
}
MyGlobalObject.KnownTypes = t.ToArray();
}
return IOChannel.KnownTypes;
}
由于我没有参与 WCF（我只需要对文件操作进行二进制序列化），因此我的解决方案可能无法完全解决 WCF 架构，但必须可以从某个地方访问序列化程序对象的构造函数。