MediaElement.NaturalDuration throws exception when querying TimeSpan.TotalSeconds

I have a winfo开发者_开发技巧rms form in which I use a MediaElement. Everything is working (more or less) perfectly. The only thing is, after loading a media file (mp3) accessing NaturalDuration.TimeSpan.TotalSeconds throws an exception

InvalidOperatoinException: A TimeSpan property can not be returned for a duration value of automatic.

(Translated from german by myself)

How can I access the timespan property? There is no special setting used in all the examples I have found (ok, they seem to be WPF native...)

I am using VisualStudio Express .Net 4, C# on Windows 7.

Any hints?

You need to wait for MediaOpened event to fire, NaturalDuration will be available after that. To check if value is available, you can use NaturalDuration.HasTimeSpan property.