public void Execute(App app, string command, IDictionary<string,object > parameters) {
if(null==app)throw new ArgumentNullException("app");
if (command.noContent()) throw new ArgumentNullException("command");
parameters = parameters ?? new Dictionary<string, object>();
var commands = new BxlParser().Parse(app.Type.Commands.Trim());
var xcmd = commands.XPathSelectElement("//command[@code='" + command + "']");
if(null==xcmd)throw new Exception("cannot find command "+command+" on app "+app.Code);
}
