web service return type exception

I have a web service and its methods return a class which is name WSResult. WSResult has 2 properties. One of property's type is int and the other one's type is object. I want to return some different type with this second property. you can see my WSREult

[Serializable]
public class WSResult
{

    public int M_Status { get; set; }
    public object M_ResultObject { get; set; }
}

But when i want to return DataSet or another serializable object with M_ResultObject, i have an error. Error is :

Sy开发者_高级运维stem.Web.Services.Protocols.SoapException: Server was unable to process request.     
---> System.InvalidOperationException: 
        There was an error generating the XML document. 
---> System.InvalidOperationException: 
        The type System.Xml.Linq.XDocument was not expected. 
        Use the XmlInclude or SoapInclude attribute to specify types that are not 
        known statically

How can i pass an object which i retrieved from other web services or that i generated from my serializable classes inside M_ResultObject property ?

KR

My manager developer solved this problem and i want to share with you. We should put

[XmlInclude(typeof(...))]

on .asmx web service and update web service reference from client side.

KR

Have you tried marking the M_ResultObject property with XmlInclude/SoapInclude as the error message hints at?

[XmlInclude(typeof(...))]
public object M_ResultObject { get; set; }

You must tell the relevant serializer what the possible types are for M_ResultObject. You can specify multiple attributes if there are multiple different objects that can be returned.