After upgrading my Silverlight 5 solution to Visual Studio 2012 (RTM), and then updating to Windows 8 (RTM), I noticed that when you set a breakpoint in XAML, you get the following tooltip in debug mode:
The breakpoint will not currently be hit. Symbol not found: System.Xml.Xsl.Runtime.XmlQueryRuntime.OnCurrentNodeChanged2.
I then tried to set a breakpoint in the XAML of a Windows Store App test project, and then of a WPF application, but I got the exact same tooltip.
I tried to repair Visual Studio 2012, but that did not change anything.
In Visual Studio 2010 such breakpoints worked fine.
Is anybody experiencing the same problem? Any idea on how to solve this?
Try to enable symbol download and source from MS. As suggested here http://msdn.microsoft.com/en-us/library/cc667410.aspx
The solution for me was opening xaml pages with the Source Code Editor.
Right-Click xaml page->Open With...-> Source Code (Text) Editor
Select the silverlight companion project of you application project.web, right click na go to properties, select the tab "WEB" then in the bottom in "Debuger" activate Silverlight check box.
来源：https://stackoverflow.com/questions/12067841/no-xaml-binding-debugging-with-breakpoints-in-visual-studio-2012-rtm-on-window