Displays a message box in front of the specified window. The message box displays a message, title bar caption, button, and icon; and accepts a default message box result, complies with the specified options, and returns a result.

public static MessageBoxResult Show( 
   Window owner,
   string messageText,
   string caption,
   MessageBoxButton button,
   MessageBoxImage icon,
   MessageBoxResult defaultResult,
   string moreInfoText,
   string helpContextID,
   string helpLinkText
)

Public Overloads Shared Function Show( _
   ByVal owner As Window, _
   ByVal messageText As String, _
   ByVal caption As String, _
   ByVal button As MessageBoxButton, _
   ByVal icon As MessageBoxImage, _
   ByVal defaultResult As MessageBoxResult, _
   ByVal moreInfoText As String, _
   Optional ByVal helpContextID As String, _
   Optional ByVal helpLinkText As String _
) As MessageBoxResult

ArcGIS.Desktop.Framework.Dialogs.MessageBox.Show("Some Message", "Some title", MessageBoxButton.YesNo, MessageBoxImage.Information, MessageBoxResult.Yes);