In NAudio, you use an implementation of the IWavePlayer class to play audio. Examples include WaveOut, WaveOutEvent, WasapiOut, AsioOut etc. To specify the audio to be played, you call the Init method passing in an IWaveProvider. And to start playing you call Play.
You can stop audio playback any time by simply calling Stop. Depending on the implementation of IWavePlayer, playback may not stop instantaneously, but finish playing the currently queued buffer (usually no more than 100ms). So even when you call Stop, you should wait for the PlaybackStopped event to be sure that playback has actually stopped.
In NAudio, the Read method on IWaveProvider is called every time the output device needs more audio to play. The Read method should normally return the requested number of bytes of audio (the count parameter). If Read returns less than count this means this is the last piece of audio in the input stream. If Read returns 0, the end has been reached.
NAudio playback devices will stop playing when the IWaveProvider's Read method returns 0. This will cause the PlaybackStopped event to get raised.
If there is any kind of audio error during playback, the PlaybackStopped event will be fired, and the Exception property set to whatever exception caused playback to stop. A very common cause of this would be playing to a USB device that has been removed during playback.
Often when playback ends, you want to clean up some resources, such as disposing the output device, and closing any input files such as AudioFileReader. It is strongly recommended that you do this when you receive the PlaybackStopped event and not immediately after calling Stop. This is because in many IWavePlayer implementations, the audio playback code is on another thread, and you may be disposing resources that will still be used.
Note that NAudio attempts to fire the PlaybackStopped event on the SynchronizationContext the device was created on. This means in a WinForms or WPF application it is safe to access the GUI in the handler.