[ServiceContract(Namespace = "")]
[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class Service1
{
[OperationContract]
public void DoWork(string name,string pwd,string email,string question,string answer)
{
MembershipCreateStatus status;
Membership.CreateUser(name, pwd,email,question,answer,true,out status);
}
// Add more operations here and mark them with [OperationContract]
}

ServiceReference2.Service1Client client = new ServiceReference2.Service1Client();
client.DoWorkAsync("xxifusi", "xxifusi345","[email protected]","q","a");