c# - List<> 包含对象的 DataContract 序列化

Question

在开发一个测试用例来理解序列化时，我遇到了一个看起来很简单但无法弄清楚的问题。我希望能够将多个对象添加到列表<>，然后序列化该列表(在本例中我使用的是 DataContractJsonSerializer)。创建对象(node1 和 node2)后，我想将它们添加到 List<> (cn) 并对其进行序列化。但是，在添加 node1 和 node2 时出现无效参数错误(“无法从‘JSON_test.Aspirate’转换为‘JSON_test.CompositeNode’)。我相信这是让数组知道基本类型的问题，但我不知道不知道该怎么做，或者这是否确实是问题所在(对这一切仍然很陌生)。

谢谢。

namespace JSON_test
{
    class Program
    {
        static void Main(string[] args)
        {
            Aspirate node1 = new Aspirate(25,40);
            Dispense node2 = new Dispense(32,50);
            ObjectToSerialize cn = new ObjectToSerialize();
            cn.CompositeNode.Add (node1);
            cn.CompositeNode.Add (node2);

            MemoryStream stream1 = new MemoryStream();
            DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(ObjectToSerialize));
            ser.WriteObject(stream1, cn.CompositeNode);
            stream1.Position = 0;
            StreamReader sr = new StreamReader(stream1);
            Console.WriteLine(sr.ReadToEnd());
            Console.ReadLine();
        }
    }

    [DataContract]
    public class ObjectToSerialize
    {
        private List<CompositeNode> compNode;
        [DataMember]
        public List<CompositeNode> CompositeNode
        {
            get {return this.CompositeNode;}
            set { this.compNode = value; }
        }

        public ObjectToSerialize()
        { 
        }
    }

    [DataContract]
    public class CompositeNode
    {

    }

    [DataContract]
    public class Aspirate
    {
        [DataMember]
        public string NodeName = "Aspirate";
        [DataMember]
        public double ZTravelHt;
        [DataMember]
        public double IndexHt;

        public Aspirate(double ZTravelHt, double IndexHt)
        {
            this.ZTravelHt = ZTravelHt;
            this.IndexHt = IndexHt;
        }
    }

    [DataContract]
    public class Dispense 
    {
        [DataMember]
        public string NodeName = "Dispense";
        [DataMember]
        public double ZTravelHt;
        [DataMember]
        public double IndexHt;

        public Dispense(double ZTravelHt, double IndexHt)
        {
            this.ZTravelHt = ZTravelHt;
            this.IndexHt = IndexHt;            
        }
    }
}

更新

namespace JSON_test
{
    class Program
    {
        static void Main(string[] args)
        {
            Aspirate node1 = new Aspirate(25,40);
            Dispense node2 = new Dispense(32,50);
            ObjectToSerialize cn = new ObjectToSerialize();
            cn.CompositeNode.Add (node1);
            cn.CompositeNode.Add (node2);

            MemoryStream stream1 = new MemoryStream();
            DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(ObjectToSerialize),
                new Type[] {typeof (Aspirate), typeof (Dispense)});
            ser.WriteObject(stream1, cn.CompositeNode);
            stream1.Position = 0;
            StreamReader sr = new StreamReader(stream1);
            Console.WriteLine(sr.ReadToEnd());
            Console.ReadLine();
        }
    }

    [DataContract]
    [KnownType(typeof(Aspirate))]
    [KnownType(typeof(Dispense))]
    public class ObjectToSerialize
    {
        private List<CompositeNode> compNode = new List<CompositeNode>();

        [DataMember]
        public List<CompositeNode> CompositeNode 
        {
            get {return this.compNode;}
            set { this.compNode = value; }
        }

        public ObjectToSerialize()
        { 

        }
    }

    [DataContract]
    [KnownType(typeof(Aspirate))]
    [KnownType(typeof(Dispense))]
    public class CompositeNode
    {

    }

    [DataContract]
    public class Aspirate : CompositeNode
    {
        [DataMember]
        public string NodeName = "Aspirate";
        [DataMember]
        public double ZTravelHt;
        [DataMember]
        public double IndexHt;

        public Aspirate(double ZTravelHt, double IndexHt)
        {
            this.ZTravelHt = ZTravelHt;
            this.IndexHt = IndexHt;
        }
    }

    [DataContract]
    public class Dispense : CompositeNode
    {
        [DataMember]
        public string NodeName = "Dispense";
        [DataMember]
        public double ZTravelHt;
        [DataMember]
        public double IndexHt;

        public Dispense(double ZTravelHt, double IndexHt)
        {
            this.ZTravelHt = ZTravelHt;
            this.IndexHt = IndexHt;            
        }
    }
}

Answer 1

您可以将 KnownTypeAttribute 添加到 ObjectToSerialize 以让序列化器知道期望的类型:

[DataContract]
[KnownType(typeof(Aspirate))]
[KnownType(typeof(Dispense))]
public class ObjectToSerialize
{
     ....
}

我知道类 Aspirate 和 Dispense 派生自 CompositeNode？这在您的代码示例中并不清楚。

顺便说一句，你的代码有错误:

get {return this.CompositeNode;}    

应该是:

get {return this.compNode;}    

更新:回应您在评论中提出的问题:您必须在 ObjectToSerialize 的构造函数中初始化集合:

public ObjectToSerialize()
{
    this.compNode = new List<CompositeNode>();
}

更新 2: 错误的行是:

ser.WriteObject(stream1, cn.CompositeNode);

这应该是:

ser.WriteObject(stream1, cn);

顺便说一句，你可以这样写:

DataContractJsonSerializer ser = new DataContractJsonSerializer(typeof(ObjectToSerialize)); 

您已经使用属性定义了已知类型。将已知类型添加到构造函数是多余的。