WCF服务对Silverlight无效

我正在尝试让WCF使用Silverlight。我是WCF的初学者,但我以前写过ASMX服务。出于某种原因,当我取消对服务中多个方法的注释时,Silverlight拒绝让我使用它,并说它无效。如果有人能帮忙,我的代码在下面。我正在使用实体框架,如果这有区别的话。

[AspNetCompatibilityRequirements(RequirementsMode = AspNetCompatibilityRequirementsMode.Allowed)]
public class MessageService {//: IMessageService {
/// <summary>
/// Sends a new message.
/// </summary>
/// <param name="recipientUsername">The recipient username.</param>
/// <param name="subject">The subject.</param>
/// <param name="messageBody">The message body.</param>
[OperationContract]
public void SendMessageByDetails(string recipientUsername, string subject, string messageBody) {
    MessageDAL.SendMessage(recipientUsername, subject, messageBody);
}

/// <summary>
/// Sends a new message.
/// </summary>
/// <param name="msg">The message to send.</param>
[OperationContract]
public void SendMessage(Message msg) {
    MessageDAL.SendMessage(msg);
}
}