Problems with External Event in modeless form

[Anonymous]

I have a code for a modeless form and I keep getting an error on starting a transaction. If I use ShowDialog it works fine. I can't seem to figure how to create a working modeless dialog for Revit.

[Transaction(TransactionMode.Manual)]
    class FormShow : IExternalCommand
    {
        public Result Execute(ExternalCommandData c, ref string m, ElementSet e)
        {
            ExternalEvent x = ExternalEvent.Create(new ExHandler());
            UIApplication u = c.Application;
            new Form1(x, u).Show();
            return Result.Succeeded;
        }
        class ExHandler : IExternalEventHandler
        {
            public void Execute(UIApplication ap) { }
            public string GetName() { "form1" }
        }
    }

    class Form1 : Form
    {
        ExternalEvent x;
        UIApplication u;
        Document d;
        public Form1(ExternalEvent e, UIApplication a)
        {
            InitializeComponent();
            x = e;
            u = a;
            d = u.ActiveUIDocument.Document;
        }
        private void Button1_Click(object sender, EventArgs e)
        {
            x.Raise();
            using (Transaction t = new Transaction(d, "command"))
            {
                t.Start();
                //do something
                t.Commit();
            }
            this.Close();
        }
    }

[Anonymous]

You'll have more answers if you post this question in the Revit API forum.

You are using a modeless form so it is not connected to revit, you cant start transactions from a modeless form.

You'll need to create an idling event and use a transaction from a command.

1 - in the command you use to show the form add an idling event

2 - create a public bool.

3 - in the form when you on click button event change the bool to true.

4 - in the idling event handling wright: if(bool){my transaction......bool = false.}

Hope it helps