This answer about P/Invoke for Shell32 reminded me of the Windows API Code Pack to access common Windows Vista/7/2008/2008R2 APIs.

It was very easy, using the PropertyEdit demo in the included samples, to figure out the Shell32 API to get various media file properties, like duration.

I assume the same prerequisite applies for having the proper demultiplexers installed, but it was quite simple, as it only required adding references to Microsoft.WindowsAPICodePack.dll and Microsoft.WindowsAPICodePack.Shell.dll and the following code:

using Microsoft.WindowsAPICodePack.Shell;
using Microsoft.WindowsAPICodePack.Shell.PropertySystem;

using (ShellObject shell = ShellObject.FromParsingName(filePath))
{
    // alternatively: shell.Properties.GetProperty("System.Media.Duration");
    IShellProperty prop = shell.Properties.System.Media.Duration; 
    // Duration will be formatted as 00:44:08
    string duration = prop.FormatForDisplay(PropertyDescriptionFormatOptions.None);
}

---

Other stuff

Some common properties for an MPEG-4/AAC audio media file:

System.Audio.Format = {00001610-0000-0010-8000-00AA00389B71}
System.Media.Duration = 00:44:08
System.Audio.EncodingBitrate = ?56kbps
System.Audio.SampleRate = ?32 kHz
System.Audio.SampleSize = ?16 bit
System.Audio.ChannelCount = 2 (stereo)
System.Audio.StreamNumber = 1
System.DRM.IsProtected = No
System.KindText = Music
System.Kind = Music

It’s easy to iterate through all properties if you’re looking for the available metadata:

using (ShellPropertyCollection properties = new ShellPropertyCollection(filePath))
{
    foreach (IShellProperty prop in properties)
    {
        string value = (prop.ValueAsObject == null) ? "" : prop.FormatForDisplay(PropertyDescriptionFormatOptions.None);
        Console.WriteLine("{0} = {1}", prop.CanonicalName, value);
    }
}