what si the meaning of a first chance exception

When I debug my code I've written in c# I get this error from a third party component:

A first chance exception of type 'System.Xm开发者_开发知识库l.XPath.XPathException' occurred in System.Xml.dll

What does this mean?

You may take a look at the following blog post which provides an overview of what first chance exceptions represent.

First-chance exceptions are special exceptions that are raised so that the debugger can break immediately. This is useful so that you can see exceptions immediately at the point they occur, and not at the point where they are caught.

If a first-chance exception is not followed by a "normal" exception that causes the debugger to break, it means that an exception was thrown and later caught (i.e., someone handled it).

Original source: http://support.microsoft.com/kb/105675

If you don't want that message, likely you can get rid of it by opening the "Exceptions" dialogue box (ctrl-alt-e) and de-selecting the "thrown" option for "Common Language Runtime Exceptions." Be prepared that the "thrown" option might be selected only for a subset of that tree entry.