WCF variable lifetime/state

Question

I'm hosting my first WCF service in IIS. I have two methods, 1 to set a string variable on the WCF Service, and the other to retrieve it. The interface used is:

[OperationContract]
string ReturnText();

[OperationContract]
void SetText(string s);

BasicHttpBinding is used. Stepping through the service with the debugger from the client reveals that the value of the string is set correctly using SetText, but when I immediately do a return text, the string is back to null.

Probably a simple one I know, but I thought that all values on the WCF service were retained between opening the service connection and closing it.

Why is the value lost between the Set and Gets?

Answer 1

By default things are session-less and instances are per-call. See

http://msdn.microsoft.com/en-us/library/ms731193.aspx

for some starter information, but in order to have state across the calls, you'll either need a PerSession or Single instancing mode on the server, and in the former case, configure the binding to support sessions (so that the two calls can be correlated as a result of being a part of the same session connection).

Answer 2

Thanks Brian, that link holds the information I need. I've added

[ServiceContract (SessionMode=SessionMode.Required)]

to my interface/contract and it automagically now works!