XmlSerialization和接口 [英] XmlSerialization and interfaces

问题描述

我知道您不能使用接口进行序列化/反序列化，但是我对所看到的行为感到困惑。

I know that you can't serialize/deserialize using an interface but I'm confused by behaviour I'm seeing.

当我反序列化并转换为接口，某些属性为null。但是，如果我将其转换回具体类型，则同一个属性是否具有值？

When I deserialize and cast back to the interface, some properties are null. But if I cast back to the concrete type the same property has a value?

因此，鉴于此XML（为简洁起见，其缩写为：）：

So, given this XML (shortened for brevity):

<Page>
  <ComponentPresentations>
    <ComponentPresentation>
      <Component>
        <Categories>
          <Category>
            <Id>tcm:35-540-512</Id>

反序列化

var serializer = new XmlSerializer(typeof(Page));
page = (IPage)serializer.Deserialize(reader);

page.ComponentPresentations[0].Component.Categories <-- is null

但是如果我强制转换回类型，

But if I cast back to the type,

var serializer = new XmlSerializer(typeof(Page));
page = (Page)serializer.Deserialize(reader);

page.ComponentPresentations[0].Component.Categories <-- is not null!

Page类型公开了接口Categories属性和非接口属性-我想避开

The Page type exposes the interface Categories property and a non-interface property - I assume to get around the serializing interface problem.

public List<Category> Categories { get; set; }
[XmlIgnore]
IList<ICategory> IComponent.Categories
{
    get { return Categories as IList<ICategory>; }
}

这是因为interface属性没有公开setter吗？

Is this because the interface property doesn't expose a setter?

推荐答案

否。问题是 Contravariance 不受 List< T> 和 IList< T> 的支持。 此处是一个很好的参考。

No. The problem is Contravariance not being supported by List<T> and IList<T>. Here is a good reference.

看看这个简单的代码：

public interface IMyInterface
{

}

public class MyImplementation : IMyInterface
{

}

List<MyImplementation> myImplementations = new List<MyImplementation>();
Console.WriteLine(myImplementations as IList<IMyInterface> == null); // OUTPUT: true!!

如您所见，类别为IList< ICategory> 将始终为null。尽管类别为IList< Category> 可以。

So as you can see, Categories as IList<ICategory> will always be null. While Categories as IList<Category> will be OK.

与序列化无关 >。

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