[mono-cecil] Cannot inject IL code into a system.web.dll...? Can it not be done...?

[jasper]

Hi,
I am was trying to inject IL code into system.web.dll, but it said
cannot disassemble assembly. I wonder why? Is it because it is
framework assembly?

I just used the AssemblyFrameworkFactory to get the
AssemblyDefinition.

           string pathBin = @"C:\WINDOWS\Microsoft.NET\Framework
\v4.0.30319\System.Web.dll";

            AssemblyDefinition assembly =
AssemblyFactory.GetAssembly(pathBin);

{"Operation is not valid due to the current state of the object."} is
the inner exception I got.

How can i get access to this assembly using Cecil?

-Jasper

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mono-cecil