private void AddBtn_OnClick(object sender, RoutedEventArgs e)
 {
     OpenFileDialog ofd = new OpenFileDialog();
     ofd.Filter = "DLL|*.dll";
     if (ofd.ShowDialog() == true)
     {
         try
         {
             Plugin plugin = new Plugin(ofd.FileName);
             _vstHost.UsedPluginCollection.Add(plugin);
             
         }
         catch (Exception ex)
         {
             MessageBox.Show("Can't open plugin.");
         }
     }
 }
 public void Add(Plugin plugin)
 {
     _plugins.Add(plugin);
 }