VSTS modal dialog close event

[javeriaanwer]

Hi,

I am using microsoft VSTS modal dialog and I want a confirmation message when modal dialog is closed from 'x' (closed button of modal dialog), I get close event which fired after event dialog is closed.

I want an event before closing the dialog. How can I do that?

here is the code:

VSS.getService(VSS.ServiceIds.Dialog).then(function(dialogService) 
{ 
       var contributionId = //id 
       var dialogOptions = { title: "ABC", close: onDialogCloseByCrossButtonClick }; 
       dialogService.openDialog(contributionId, dialogOptions).then(
               function (dialog) {
                    // do something
        });
}

like its appearing in TFS WorkItem window.