Called before the MouseLeftButtonDown event occurs.
Assembly: System.Windows (in System.Windows.dll)
The method is called before any event handler for the MouseLeftButtonDown event is called. This method allows derived classes to handle the MouseLeftButtonDown event without attaching a delegate. This is the preferred technique for handling the event in a derived class.
RichTextBox handles cursor placement and selection in MouseLeftButtonDown event. RichTextBox attempts to capture the mouse in its MouseLeftButtonDown event handler. Mouse capture is needed for extending the selection by using the mouse. Mouse capture is released in the RichTextBox's MouseLeftButtonUp event handler. If you capture the mouse on another UIElement's MouseLeftButtonDown handler, extending the selection by using a mouse in the RichTextBox control will not work.Notes to Inheritors
When overriding the method in a derived class, be sure to call the base class’s method so that registered delegates receive the event.
For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.