Can I serialize an ExpandoObject in .NET 4?

Question

I'm trying to use a System.Dynamic.ExpandoObject so I can dynamically create properties at runtime. Later, I need to pass an instance of this object and the mechanism used requires serialization.

Of course, when I attempt to serialize my dynamic object, I get the exception:

System.Runtime.Serialization.SerializationException was unhandled.

Type 'System.Dynamic.ExpandoObject' in Assembly 'System.Core, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' is not marked as serializable.

Can I serialize the ExpandoObject? Is there another approach to creating a dynamic object that is serializable? Perhaps using a DynamicObject wrapper?

I've created a very simple Windows Forms example to duplicate the error:

using System;
using System.Windows.Forms;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Dynamic;

namespace DynamicTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {            
            dynamic dynamicContext = new ExpandoObject();
            dynamicContext.Greeting = "Hello";

            IFormatter formatter = new BinaryFormatter();
            Stream stream = new FileStream("MyFile.bin", FileMode.Create,
                                           FileAccess.Write, FileShare.None);
            formatter.Serialize(stream, dynamicContext);
            stream.Close();
        }
    }
}

Hayashi

Short of implementing a manual serialisation routine, I'm inclined to say that if it's not marked Serializable then, no, quite simply. – Whimwham

Answer 1

I can't serialize ExpandoObject, but I can manually serialize DynamicObject. So using the TryGetMember/TrySetMember methods of DynamicObject and implementing ISerializable, I can solve my problem which was really to serialize a dynamic object.

I've implemented the following in my simple test app:

using System;
using System.Windows.Forms;
using System.IO;
using System.Runtime.Serialization;
using System.Runtime.Serialization.Formatters.Binary;
using System.Collections.Generic;
using System.Dynamic;
using System.Security.Permissions;

namespace DynamicTest
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {            
            dynamic dynamicContext = new DynamicContext();
            dynamicContext.Greeting = "Hello";
            this.Text = dynamicContext.Greeting;

            IFormatter formatter = new BinaryFormatter();
            Stream stream = new FileStream("MyFile.bin", FileMode.Create, FileAccess.Write, FileShare.None);
            formatter.Serialize(stream, dynamicContext);
            stream.Close();
        }
    }

    [Serializable]
    public class DynamicContext : DynamicObject, ISerializable
    {
        private Dictionary<string, object> dynamicContext = new Dictionary<string, object>();

        public override bool TryGetMember(GetMemberBinder binder, out object result)
        {
            return (dynamicContext.TryGetValue(binder.Name, out result));
        }

        public override bool TrySetMember(SetMemberBinder binder, object value)
        {
            dynamicContext.Add(binder.Name, value);
            return true;
        }

        [SecurityPermissionAttribute(SecurityAction.Demand, SerializationFormatter = true)]
        public virtual void GetObjectData(SerializationInfo info, StreamingContext context)
        {
            foreach (KeyValuePair<string, object> kvp in dynamicContext)
            {
                info.AddValue(kvp.Key, kvp.Value);
            }
        }

        public DynamicContext()
        {
        }

        protected DynamicContext(SerializationInfo info, StreamingContext context)
        {
            // TODO: validate inputs before deserializing. See http://msdn.microsoft.com/en-us/library/ty01x675(VS.80).aspx
            foreach (SerializationEntry entry in info)
            {
                dynamicContext.Add(entry.Name, entry.Value);
            }
        }

    }
}

and Why does SerializationInfo not have TryGetValue methods? had the missing puzzle piece to keep it simple.

Hayashi

Had some doubts about answering my own question, but it seems to be encouraged: meta.stackexchange.com/questions/9933/… – Hayashi

will it be possible to do it also for a custom serialization library ? For example versatile Serilization in my case ? – Flat

Answer 2

ExpandoObject implements IDictionary<string, object>, e.g.:

class Test
{
    static void Main()
    {
        dynamic e = new ExpandoObject();
        e.Name = "Hello";

        IDictionary<string, object> dict = (IDictionary<string, object>)e;

        foreach (var key in dict.Keys)
        {
            Console.WriteLine(key);
        }

        dict.Add("Test", "Something");

        Console.WriteLine(e.Test);

        Console.ReadKey();
    }
}

You could write the contents of the dictionary to a file, and then create a new ExpandoObject through deserialisation, cast it back to a dictionary and write the properties back in?

Ozuna

If the output has to be in XML then IDictionary<,> can't be serialized with XmlSerializer but it can be serialized with DataContractSerializer though the output is too verbose. Personally I think JsonFx mentioned in other answer does better job serializing ExpandoObject. – Determinism

Answer 3

Maybe a bit late to answer but I use jsonFx to serialize and deserialize expandoObjects and it works very well :

serialization:

dim XMLwriter As New JsonFx.Xml.XmlWriter
dim serializedExpando as string =XMLwriter.Write(obj)

deserialization

dim XMLreader As New JsonFx.Xml.XmlReader
Dim obj As ExpandoObject = XMLreader.Read(Str)

Salian

Beautiful. The JsonWriter just saved me a ton of time! Here is the Git for JsonFx if anyone needs it: github.com/jsonfx/jsonfx – Anesthetic

i tried this. It works perfectly for serializing the dynamic object, but the deserialization shows an exception : Expected Object Property Name or end of object(Object Begin). – Footrace

Use JsonReader and Writer instead of Xml to fix the above exception :) – Davey