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Editorial Team
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Asked: 2026-05-24T12:29:31+00:00

I am using asp.net mvc2 and mef to create pluggable architecture from this article

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I am using asp.net mvc2 and mef to create pluggable architecture from this article
When i deploy my project on real iis (7.0, windows 2008 server) i always got an mef exception at first request from client browser:

global.asax
System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Lazy`1.get_Value() in c:\dev\mef\MEF_SVN\tags\Preview6\src\ComponentModel\System\Lazy.cs:line 61
   at System.ComponentModel.Composition.ReflectionModel.ReflectionModelServices.LazyExportDefinition.get_Metadata() in c:\dev\mef\MEF_SVN\tags\Preview6\src\ComponentModel\System\ComponentModel\Composition\ReflectionModel\ReflectionModelServices.cs:line 345

Cant understand how to fix it. Thanks for all responses and ideas.

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1 Answer

  1. Editorial Team

    Without a bit more code it’s quite hard to debug. I would hazard a guess and say that you are using an early build of MEF (for the .NET v2.0/3.5 platform). I’ve done some previous work with ASP.NET MVC and MEF:

    1. Modular ASP.NET MVC using the Managed Extensibility Framework (MEF), Part One
    2. Modular ASP.NET MVC using the Managed Extensibility Framework (MEF), Part Two
    3. Modular ASP.NET MVC using the Managed Extensibility Framework (MEF), Part Three

    and

    1. MVC3 and MEF

    It’s worth investigating the differences between these different implementations, and its also worth making sure you are actually using a version of MEF that is more or less feature complete (the one attached to my project above is an example).

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