IFormatter formatter = new BinaryFormatter();
        String directorio = Environment.CurrentDirectory + "..\Listas";

            PARA GUARDAR
                saveFileDialog1.InitialDirectory = directorio;
                saveFileDialog1.FileName = "";
                saveFileDialog1.Filter = "(*.btn)|*.btn";
                if (saveFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                {
                    Stream stream = new FileStream(saveFileDialog1.FileName, FileMode.Create, FileAccess.Write, FileShare.None);
                    formatter.Serialize(stream, "TU OBJETO DE LA CALSE VA AQUI");
                    stream.Close();
                }
                break;

            PARA ABRIR
                openFileDialog1.FileName = "";
                openFileDialog1.Filter = "(*.btn)|*.btn";
                openFileDialog1.InitialDirectory = directorio;
                if (openFileDialog1.ShowDialog() == System.Windows.Forms.DialogResult.OK)
                {
                    g.Clear(BackColor);
                    grafo.Clear();
                    Stream stream = new FileStream(openFileDialog1.FileName, FileMode.Open, FileAccess.Read, FileShare.None);
                    grafo = ("TU OBJETO DE LA CALSE VA AQUI")formatter.Deserialize(stream);
                    stream.Close();

                    "AQUI RECONSTRUYES TODOS TUS BOTONES, YA QUE UN OBJETO BOTON NO ES SERIALIZABLE"
                    Invalidate();
                }