Silverlight 2 application code is compiled to Common IL and packaged into assemblies (.dll) which are in turn deflated into a Zip file (container with .xap extension). The IL is a CPU- and platform- independent instruction set. The Silverlight runtime has in it the Core CLR which executes this IL. Given that .NET Framework involves much of the same things save for the .xap packaging, how does one tell between a DLL built for Silverlight versus one for .NET Framework? Well, the answer is in one of the security assumptions that Silverlight's Core CLR makes to distinguish a core platform assembly from a transparent code app assembly. The mscorlib.dll in Silverlight is signed with a different key than it's namesake in .NET Framework. This is apparent in it's full name, or specifically it's public key token. The public key token for mscorlib in Silverlight is: 7cec85d7bea7798e while the public key token for mscorlib in .NET Framework is: b77a5c561934e089 So the trick to sniffing out an arbitrary
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