Call stack window always empty

After being introduced to the call stack window by this ASP.NET MVC video I've attempted to understand how it works.

My开发者_JS百科 understanding was that it shows all of the method calls - in the order they were called. However its always blank whilst I'm debugging - am I doing something wrong?

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Ahh - As is usually the case once I've asked a question I work it out!

Its turns out it is only shown when a breakpoint has been hit