Is it possible to return an ExpandoObject from a web service call?

I would like to return ExpandoObject from WebMethod, for example:

public ExpandoObject TestMethod(int val)
     dynamic item = new ExpandoObject();

     item.Value = val;
     item.SomeOtherStuff = "SomeOtherStuff";


     return item;


When I try to do this, I get this error:

To be XML serializable, types that inherit from IEnumerable must have an Add (System.Object) implementation

And I cannot extend the ExpandoObject class as it is sealed.

Is there another way to do this?


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1 answer

You can create your own serializable version of ExpandoObject by inheriting from DynamicObject and implementing ISerializable .

ExpandoObject is basically a dictionary that stores the names of dynamically attached properties along with values:

public class SerializableExpandoObject : DynamicObject, ISerializable
    private Dictionary<string, object> properties = new Dictionary<string, object>()

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

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



You can implement any serialization format you need to support here, including IXmlSerializable .



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