[PluginAttribute("MessageSenderReceiver.MessageReceiver",     //Plugin name
                 "ADSK")]                                     //4 character Developer ID or GUID
[AddInPluginAttribute(AddInLocation.None)]                    //Identifies this as an Addin Plugin, that will not display in the ribbon
public class MessageReceiver : AddInPlugin                    //Derives from AddInPlugin
{
   public override int Execute(params string[] parameters)
   {
      //initialise a buffer to store the message
      String buffer = string.Empty;

      //Iterate the parameters and build the complete message
      foreach (String param in parameters)
      {
         buffer = buffer + "\r\n" + param;
      }

      //create the dialog to display to the user
      MessageReceived messageReceived = new MessageReceived();

      //assign the message to be displayed
      messageReceived.Message = buffer;

      //Show the dialog
      messageReceived.ShowDialog(Autodesk.Navisworks.Api.Application.Gui.MainWindow);

      //return the the caller the value given by the user
      return messageReceived.ReturnValue;
   }
}