in the process of creating a WCF service I ran into a term that's new to me. Basically when specifying the `InstanceContextMode` I have a few options, including; `PerSession`, `PerCall` and `Single`. Here's the code from the sample I'm learning from:

```
[ServiceBehavior(InstanceContextMode=InstanceContextMode.Single)]
public class EvalService : IEvalService { ...

```

Now, he stated by doing this that only one instance of my service would be created at runtime. What does this mean? I thought that everytime a connection was made to the web service that it was treated as a seperate instance.

Does it persist, this instance of my service, for every request made? Judging by the other members mentioned in the [docs](http://msdn.microsoft.com/en-us/library/system.servicemodel.instancecontextmode.aspx), is it safe to assume this is the way it works?