An object that is passed to your application when a dialog is displayed in Revit. 
   Namespace:   Autodesk.Revit.UI.Events  
  Assembly:   RevitAPIUI  (in RevitAPIUI.dll) Version: 2015.0.0.0 (2015.0.0.0) 
Syntax
Remarks
 When the application receives this object, a dialog has been displayed in Revit that requires user interaction. The OverrideResult function can be used to cause the dialog to be dismissed and return a desired result code. 
 Inheritance Hierarchy
  System Object  
Autodesk.Revit.DB APIObject
Autodesk.Revit.UI.Events DialogBoxData
Autodesk.Revit.UI.Events MessageBoxData
 
 Autodesk.Revit.DB APIObject
Autodesk.Revit.UI.Events DialogBoxData
Autodesk.Revit.UI.Events MessageBoxData