Deserialization onto existing objects [edit] IL & Intercepting Method Calls

See more:

C#

.NET

WCF

I am passing data back and forth between server and client.
The easy part: In the deserialization, I would like to check to see if the not yet fully deserialized object already exists here. If the object is already here, it could well be referenced by other objects, so all the data in the arriving object has to be copied to the existing one.
Hard part: Once I know the object already exists, I would like to deserialize over the existing object instead of finishing the deserialization on the current object and then moving the data.
So, the question:
Can I hijack the deserialization process and put the data directly into the existing object instead of the one being created by the deserializer?
[edit]
Looking at the IL for ctor, it pushes 'this' onto the stack and calls the base ctor.[^]
While I can not (?) replace 'this' locally, I could intercept the call, and push the old object onto the stack, instead of the new one. All the deserialization would be done on it, instead of the new one. I could just discard the new object after deserialization, since the old one would now have all the values deserialized onto it.
New questions:
Anyone know how to use reflection to intercept a method call, basically substituting one method call for another?
Anyone know of a how to site for using IL in C# methods?
I need a facilitator! :-D
Thanks
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