【单项选择题】
You are developing a client application that consumes a Windows Communication Foundation (WCF) service. You use the svcutil.exe utility to create a proxy for the service. You use the svcutil.exe switches that generate asynchronous calls. GetFlight is a service operation that takes no parameters and returns a string. The GetFlightCallback method must be called when the service operation returns.You create an instance of the client proxy with the following code:var client = new TranvelServiceClient();You need to ensure that a callback is received when the GetFlight operation is called asynchronously.<br /> Which code segment should you use?（）<p> You are developing a client application that consumes a Windows Communication Foundation (WCF) service. You use the svcutil.exe utility to create a proxy for the service. You use the svcutil.exe switches that generate asynchronous calls. GetFlight is a service operation that takes no parameters and returns a string. The GetFlightCallback method m
A、A. client.BeginGetFlight(GetFlightCallback, null); client.GetFlight();
B、B. client.GetFlight(); client.BeginGetFlight(GetFlightCallback, null);
C、C. client.GetFlightCompleted += new EventHandler(GetFlightCallback); client.GetFlightAsync();
D、D. IAsyncResult asyncResult = client.BeginGetFlight(GetFlightCallback, client); client.EndGetFlight(asyncResult);
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