When customizing mobile application, most of the time you navigate user from one Page to the other in order to complete a workflow. In some cases, however, you might want to show user a customized dialog-style page. An example would be showing user the settings dialog for built-in Gps, or a login dialog collecting user's credentials right after the application launches.

The Dialog is meant to be used when you need to gather input from users, and decide where to navigate them to based upon the inputs you gathered.

Note that mobile application framework provides EditAttributesPage so you can use it to show a dialog for attribute editing. You can also create your own dialog with additional implementations by inheriting Dialog class.

System.Object
   System.MarshalByRefObject
      System.ComponentModel.Component
         System.Windows.Forms.Control
            System.Windows.Forms.ScrollableControl
               System.Windows.Forms.ContainerControl
                  System.Windows.Forms.Form
                     ESRI.ArcGIS.Mobile.Client.MobileForm
                        ESRI.ArcGIS.Mobile.Client.Dialog
                           ESRI.ArcGIS.Mobile.Client.Dialogs.DeleteProjectsDialog

Reference