MSDN Magazine - September 2008 - (Page 21)

As you may have deduced, then, unhandled exceptions are good in that they will help you better understand the reason for a crash. In fact, this should also indicate to you that using patterns like catch(Exception ex) are bad since they imply that you will catch any managed exception, which is semantically similar to what the CLR did in versions 1.0 and 1.1. Such patterns should be replaced with those that have a more specific exception type and should be as close to the source of the exception as possible. The further away you catch the exception from the point it was raised, the less context you will have about the cause of the exception. Guerrilla .NET: w/ 3.0 & 3.5 content September 15th-19th Los Angeles Unhandled Exceptions on Non-CLR-Created Threads Call 800.699.1932 to register today! or visit www.develop.com Figure 4 illustrated the case of a thread that was created out- New Hands-on .NET 3.0/3.5 Training What’s New in .NET 3.0-3.5 w/LINQ September 22nd - Los Angeles October 6th - Boston side the CLR and later entered in to execute managed code. In the example, if the exception was not handled even in the FirstFunc method, the exception would exit the CLR but continue to propagate up the stack as a native SEH exception (managed exceptions are represented as native SEH exceptions). This propagation is per- Windows Communication Foundation w/ 3.5 content September 15th - Chicago September 29th - Austin October 13th - Los Angeles Unhandled exceptions can help you better understand the reason for a crash. formed by the OS as it goes about looking for an exception handler. Examples of such threads include the entry point thread (a native thread that calls into managed code using a pointer to a delegate), native threads that use COM interop, or the CLR Hosting API. In this case two things can happen. First, the OS could find an SEH exception handler in one of the native frames in the user (or CLR) code. This would result in a second pass of SEH exception handling to run the finally clauses from the frame in which the exception was raised all the way up to the point just before the exception handler that agreed to handle the exception. Once that step is complete, execution is resumed in the exception handler (for example, a catch clause) that caught the exception. Native threads that enter the CLR using the hosting API or COM interop to execute managed code fall into this category. The second possible outcome is that the OS will not be able to find an SEH exception handler even in the top-most native frame in user code. If this happens, the exception is deemed unhandled and the OS triggers its own unhandled exception processing mechanism that the CLR relies on to, in turn, trigger its unhandled exception processing. Native threads that invoke managed delegates outside the protection of any native exception handling, using the pointer obtained from the Marshal.GetFunctionPointerForDelegate managed API, fall into this category. The OS unhandled exception filter (UEF) mechanism may not always result in triggering the CLR’s unhandled exception processing. Before I explain, let’s see how the OS’s UEF mechanism works. msdnmagazine.com Windows Presentation Foundation w/ 3.5 content September 15th - Boston September 29th - Bellevue October 13th - Los Angeles Windows WorkFlow Foundation September 8th - Boston NEW COURSE Essential Skills for the Business Analyst October 29th - Los Angeles On-Site Training For groups of students, DevelopMentor’s On-Site course delivery may offer the most cost-effective solution – at your location, at the time you need it. OnSites also offer the ability to customize a course to your group’s needs, including course content, labs that run on your programming platform and lab exercises tailored to your business or project. Call us today to discuss your training needs! US -800.699.1932 UK -(0)8000.562.265 Europe-(0)01242.525.108 September 2008 21 http://www.develop.com http://www.develop.com http://msdnmagazine.com

Table of Contents Feed for the Digital Edition of MSDN Magazine - September 2008

MSDN Magazine - September 2008 Contents Toolbox CLR Inside Out Data Points Advanced Basics Office Space Cutting Edge Hierarchy ID New Features for Microsoft SQL Server 2008 Prism Data Services Advanced WPF Test Run Security Briefs Foundations { End Bracket }

MSDN Magazine - September 2008

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