Return Serializable Object From FileStream?

I'm a little green when it comes to streaming and serialization...but what i wanna do is make the Upload method on the server return a serializable object to the client (it is void right now). I have a public class ServiceResult that i decorate with [Serializable], and a public class FileTransferService that implements IFileTransferService

[ServiceContract()]
public interface IFileTransferService
{
[OperationContract(IsOneWay = false)]
string Upload(FileTransferRequest request);
}
The implementation does its thing, and then at the end i create and serialize the object and try to return the string
return ServiceResultSerializer.SerializeAnObject(result);
On the client side i call this service using this class
[System.CodeDom.Compiler.GeneratedCodeAttribute("System.ServiceModel", "3.0.0.0")]
[System.ServiceModel.ServiceContractAttribute(ConfigurationName = "IFileTransferService")]
public interface IFileTransferService
{
// CODEGEN: Generating message contract since the wrapper name (FileTransferRequest) of message FileTransferRequest does not match the default value (Upload)
[System.ServiceModel.OperationContractAttribute(IsOneWay = false, Action = "http://tempuri.org/IFileTransferService/Upload")]
string Upload(FileTransferRequest request);
}

I'm basically taking this project found on this blog: [URL] And trying to make it return a value that the client caller can use I get an error right now that says: The operation 'Upload' could not be loaded because it has a parameter or return type of type System.ServiceModel.Channels.Message or a type that has MessageContractAttribute and other parameters of different types. When using System.ServiceModel.Channels.Message or types with MessageContractAttribute, the method must not use any other types of parameters. Which i have no idea what it means :P I think cuz im trying to change the Service paramaters.