直接使用Exception进行捕获，然后在监视器中查看具体是哪一个异常

System.Exception {System.ServiceModel.Security.MessageSecurityException}

查看StackTrace

Server stack trace:
在 System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.ProcessReply(Message reply, SecurityProtocolCorrelationState correlationState, TimeSpan timeout)
在 System.ServiceModel.Channels.SecurityChannelFactory`1.SecurityRequestChannel.Request(Message message, TimeSpan timeout)
在 System.ServiceModel.Security.SecuritySessionSecurityTokenProvider.DoOperation(SecuritySessionOperation operation, EndpointAddress target, Uri via, SecurityToken currentToken, TimeSpan timeout)
在 System.ServiceModel.Security.SecuritySessionSecurityTokenProvider.GetTokenCore(TimeSpan timeout)
在 System.IdentityModel.Selectors.SecurityTokenProvider.GetToken(TimeSpan timeout)
在 System.ServiceModel.Security.SecuritySessionClientSettings`1.ClientSecuritySessionChannel.OnOpen(TimeSpan timeout)
在 System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
在 System.ServiceModel.Channels.ServiceChannel.OnOpen(TimeSpan timeout)
在 System.ServiceModel.Channels.CommunicationObject.Open(TimeSpan timeout)
在 System.ServiceModel.Channels.ServiceChannel.CallOnceManager.CallOnce(TimeSpan timeout, CallOnceManager cascade)
在 System.ServiceModel.Channels.ServiceChannel.EnsureOpened(TimeSpan timeout)
在 System.ServiceModel.Channels.ServiceChannel.Call(String action, Boolean oneway, ProxyOperationRuntime operation, Object[] ins, Object[] outs, TimeSpan timeout)
在 System.ServiceModel.Channels.ServiceChannelProxy.InvokeService(IMethodCallMessage methodCall, ProxyOperationRuntime operation)
在 System.ServiceModel.Channels.ServiceChannelProxy.Invoke(IMessage message)

Exception rethrown at [0]:
在 System.Runtime.Remoting.Proxies.RealProxy.HandleReturnMessage(IMessage reqMsg, IMessage retMsg)
在 System.Runtime.Remoting.Proxies.RealProxy.PrivateInvoke(MessageData& msgData, Int32 type)
在 Client.localhost.IObtainData.SelectUserByName(String userName)
在 Client.localhost.ObtainDataClient.SelectUserByName(String userName) 位置 d:\Colleague\BaiYongsheng\Server\Client\Service References\localhost\Reference.cs:行号 71
在 Client.Program.Main(String[] args) 位置 d:\Colleague\BaiYongsheng\Server\Client\Program.cs:行号 23