Principal.cs

using System;
using System.Windows.Forms;

namespace R811ReproducirMP3
{
    public partial class Principal : Form
    {
        public Principal()
        {
            InitializeComponent();
        }

        private void btnReproducirMp3_Click(object sender, EventArgs e)
        {
            OpenFileDialog ofd = new OpenFileDialog();
            ofd.Filter = "Media Files|*.wav;*.mp3;*.mp3;*.wma|All Files|*.*";

            if (DialogResult.OK == ofd.ShowDialog())
            {
                QuartzTypeLib.FilgraphManager graphManager = new QuartzTypeLib.FilgraphManager();
                QuartzTypeLib.IMediaControl mc = (QuartzTypeLib.IMediaControl) graphManager;

                mc.RenderFile(ofd.FileName);

                mc.Run();
            }
        }
    }
}