c# - WebAPI 在返回 JSON 而不是 XML 时正确序列化从抽象类型派生的类

Question

我的模型:

    public abstract class BaseClass
    {
        public string id { get; set; }    
    }

    [KnownType(typeof(BaseClass))]
    public class ChildClass1 : BaseClass
    {
        public string shape { get; set; }
    }

    [KnownType(typeof(BaseClass))]
    public class ChildClass2: BaseClass
    {
        public string color { get; set; }
    }

    public class Widget
    {
        public List<BaseClass> Contents { get; set; }
        public Widget()
        {
            Contents = new List<BaseClass>();
        }    
    }

我的网络 API 端点:

        [HttpGet]
        public Widget Get()
        {
            Widget widget = new Widget();
            ChildClass1 cc1 = new ChildClass1();
            cc1.id = "1234";
            cc1.shape = "round";
            ChildClass2 cc2 = new ChildClass2();
            cc2.id = "4321";
            cc2.color = "red";
            widget.Contents.Add(cc1);
            widget.Contents.Add(cc2);
            return widget;
        }

当请求输出为 XML 时，它在序列化我的派生类时遇到问题。

The 'ObjectContent`1' type failed to serialize the response body for content type 'application/xml; charset=utf-8'.

Type 'WebApplication1.Models.ChildClass1' with data contract name 'ChildClass1:http://schemas.datacontract.org/2004/07/WebApplication1.Models' is not expected. Consider using a DataContractResolver if you are using DataContractSerializer or add any types not known statically to the list of known types - for example, by using the KnownTypeAttribute attribute or by adding them to the list of known types passed to the serializer.

Answer 1

您应该将 KnownType 属性添加到 Widget 类，并指定所有可能的类型，这些类型可以作为 Contents< 的 BaseClass 实例传递 列表:

[KnownType(typeof(ChildClass1))]
[KnownType(typeof(ChildClass2))]
public class Widget
{        
    public List<BaseClass> Contents { get; set; }
    public Widget()
    {
        Contents = new List<BaseClass>();
    }
}

序列化响应:

<Widget xmlns:i="http://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://schemas.datacontract.org/2004/07/YourNamespace">
    <Contents>
        <BaseClass i:type="ChildClass1">
            <id>1234</id>
            <shape>round</shape>
        </BaseClass>
        <BaseClass i:type="ChildClass2">
            <id>4321</id>
            <color>red</color>
        </BaseClass>
    </Contents>
</Widget>