I am writing a SOAP based ASP.NET Web Service having a number of methods to deal with Client objects. e.g:

• int AddClient(Client c) => returns Client ID when successful
• List GetClients()
• Client GetClientInfo(int clientId) In the above methods, the return value/object for each method corresponds to the "all good" scenario i.e. A client Id will be returned if AddClient was successful or a List<> of Client objects will be returned by GetClients. But what if an error occurs, how do I convey the error message to the caller?

I was thinking of having a Response class: Response { StatusCode, StatusMessage, Details } where Details will hold the actual response but in that case the caller will have to cast the response every time. What are your views on the above? Is there a better solution?