Extracted from MSDN:
One frequent application of routed events within the WPF platform is for input events. In WPF, tunneling routed events names are prefixed with the word "Preview" by convention. Input events often come in pairs, with one being the bubbling event and the other being the tunneling event. For example, the KeyDown event and the PreviewKeyDown event have the same signature, with the former being the bubbling input event and the latter being the tunneling input event. Occasionally, input events only have a bubbling version, or perhaps only a direct routed version. In the documentation, routed event topics cross-reference similar routed events with alternative routing strategies if such routed events exist, and sections in the managed reference pages clarify the routing strategy of each routed event.
Try to add preview mouseleftbuttondown and mouseleftbuttondown, see what will happen?
转载于:https://www.cnblogs.com/pangpangxiong/archive/2009/08/18/1548877.html