var res = new FormDialog<SuperChoice>(new SuperChoice(), SuperChoice.BuildForm,FormOptions.PromptInStart);
await context.PostAsync(res.ToString());
context.Call(res, ChoiceSelected);

var bookingform = await result;
if(bookingform.Choice.ToString().Equals("Leave"))
{
   var res1 = new FormDialog<Leave_choice>(new Leave_choice(), Leave_choice.BuildForm, FormOptions.PromptInStart);
   context.Call(res1, LeaveSelected);
}
//various other choices

var leave_form = await result1;
//process leave request
await context.PostAsync("Leave request submitted.");

var leave_form = await result1;