如何使用填充了数组的对象类型的属性来序列化类

Question

After searching 99% of the net I am still stuck on the following matter. I have a web service which must comply to a wsdl that a partner company supplied. Calling a method of this service results in a (complex) class. Unfortunately a serialization error is raised when the service is called.

I have pinpointed the issue but cannot think of (and find) a solution to it. Because I'm dependant on the wsdl which was supplied, I cannot change the complex class structure. Hope anyone knows what I am missing. Here is example code to reproduce my issue:

[System.SerializableAttribute()]
public class MyObject
{
    public int Id { get; set; }
    public object Item { get; set; }    // <---- Note type *object* here
}

[System.SerializableAttribute()]
public class MyItem
{
    public int Id { get; set; }
    public string Name { get; set; }
}

[TestClass]
public class SerializationTest
{
    [TestMethod]
    public void Serializing()
    {
        MyObject myObject = new MyObject { Id = 1 };
        myObject.Item = new MyItem[] { new MyItem { Id = 1, Name = "Test" } };

        string serializedString = SerializeObjectToXmlString(myObject, new []{ typeof(MyItem)});

        Assert.IsFalse(String.IsNullOrWhiteSpace(serializedString));
    }

    /// <summary> 
    /// This method serializes objects to an XML string using the XmlSerializer 
    /// </summary> 
    private static string SerializeObjectToXmlString(object theObject, Type[] types)
    {
        using (var oStream = new System.IO.MemoryStream())
        {
            var oSerializer = new System.Xml.Serialization.XmlSerializer(theObject.GetType(), types);

            oSerializer.Serialize(oStream, theObject);  // <- Here the error is raised

            return System.Text.Encoding.Default.GetString(oStream.ToArray());
        }
    }
}

In the Try/Catch an error is raised after calling method Serialize(). Details of this error are:

InvalidOperationException was unhandled by user code
- There was an error generating the XML document.
  The type MyItem[] may not be used in this context.

My development context consists of Visual Studio 2010, .Net Framework 3.5.

Edit #1: Added Serialization attributes but the error remaines

Answer 1

It appears that you cannot add an array of types to an object and serialize it. The solution was to create a container class which - like the name says - contains the array. This way you can assign the container class to the object and serialize it all.

In addition to my case, I was mislead by the object model created by the wsdl.exe utility, since the container class is only a technical solution to add an array to an object . This container class was also created so everything was already there to use. Only after trying out my custom container class I noticed the already created container class. Lost a lot of time on this matter unfortunately...

Answer 2

This is an old question, but I had the same problem and found a different solution, so I thought I'd share in case it helps someone else.

I found that I could add attributes to allow arrays of specific types. For the problem above, the MyObject class could be edited as below:

[System.SerializableAttribute()]
public class MyObject
{
    public int Id { get; set; }
    [XmlElement(Type = typeof(object), ElementName = "Item"), //added
        XmlElement(Type = typeof(MyItem[]), ElementName = "Item_asArrayOfMyItem")] //added
    public object Item { get; set; }    // <---- Note type *object* here
}

Anything that serialized before will still look the same, but now MyObject can be serialized even when Item has type MyItem[] , as in the question's test case.

Answer 3

You should mark you classes as

[Serializable]
public class MyObject
{
  public int Id { get; set; }
  public MyItem[] Item { get; set; }    // <---- Note type *object* here
}

[Serializable]
public class MyItem
{
  public int Id { get; set; }
  public string Name { get; set; }
}

Serialize uknown object ( Item of MyObject class) you will need to do manually by implementing proper interfaces: ISerializable and IDeserializationCallback , botha added to MyObject class.