How play a .mp3 (or other) file in a UWP app?

You cannot just read any file on your file system like this with windows store applications.

If you just want to test it:

1. Add the file to your project in Visual Studio
2. Change your file’s "Build Action" to "Content".
3. Change "Copy to Output Directory" to "Copy Always".

What you probably want to do is explained in the section, Read Local files w/o a Picker from this article. This might also be helpful.

Every Windows Store App has three folders. A Local folder, a Roaming folder and a Temp folder. Each is accessed the same way. Local is meant to store assets in a local, application-specific folder.

Here is the answer:

StorageFolder Folder = Windows.ApplicationModel.Package.Current.InstalledLocation;
                Folder = await Folder.GetFolderAsync("MyFolder");
                StorageFile sf = await Folder.GetFileAsync("MyFile.mp3");
                PlayMusic.SetSource(await sf.OpenAsync(FileAccessMode.Read), sf.ContentType);
                PlayMusic.Play();

MfG.