WCF Dictionary<string, object> serialization

I have a service that has a method like this

  [ServiceContract(Namespace = "")]
    [AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
    public class MyService
    {
        [OperationContract]
        public object MyMethod(string param1, string param2, object[] myarray)
        {
            //do stuff
            return result;
        }
     }

I call my method from my code like this:

public Dictionary<string, object> MyDictionary{ get; set; }
serv.MyMethodCompleted += new EventHandler<MyServiceReference.MyMethodCompletedEventArgs>(serv_MyMethodCompleted);
serv.MyMethodAsync("param1","param2",  new ObservableCollection<object>(){MyDictionary});


void serv_MyMethodCompleted(object sender, MyServiceReference.MyMethodCompletedEventArgs e)
{
    //Happy happy joy joy
}

Everithing craches with this error:

There was an error while trying to serialize parameter :myarray. The InnerException message was 'Type 'System.Collections.Generic.Dictionary`2[[System.String, mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e],[System.Object, mscorlib, Version=2.0.5.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]]' with data contract name 'ArrayOfKeyValueOfstringanyType:http://schemas.microsoft.com/2003/10/Serialization/Arrays' is not expected. 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 DataContractSerializer.'. Please see InnerException for more details.开发者_开发百科

 public System.IAsyncResult BeginCallMethod(string param1, string param2, System.Collections.ObjectModel.ObservableCollection<object> myarray, System.AsyncCallback callback, object asyncState) {
                object[] _args = new object[3];
                _args[0] = param1;
                _args[1] = param2;
                _args[2] = myarray;
                System.IAsyncResult _result = base.BeginInvoke("MyMethod", _args, callback, asyncState); <--here it craches
                return _result;
            }

what did I did wrong? how can I fix this?

---

The myArray parameter and the return value needs to be a strongly typed and attributed with DataContract and DataMember attributes. The myArray should be collection like IEnumerable<Item> that can be serialized:

[DataContract]
class Item
{
    [DataMember]
    public string Name {get;set;}

    [DataMember]
    public double Cost {get;set;}
}