If you drag a movie into Microsoft expression encoder, not only can you add the movie and set metadata and otherwise manipulate the media, but you can also choose a template for the output that includes a Silverlight player that encoder will create as part of its output. You can use this player as-is, or you can edit it in Visual Studio to your own specification.
Even this starter player can save you a great deal of hand coding and make the creation of a complex video player a simple task.
You can see an illustration of how to do this in our learning video on the creation of a hyper-video player, and you may want to review our two-part series on creating a full video player here and here.