C# 4.0's major themes are interoperability with dynamic programming paradigms and improved Office programmability. Dynamic lookup, a new feature in C# 4.0, allows you to use and manipulate an object from IronPython, IronRuby, JScript, the HTML DOM, or a standard .Net library in the same way, no matter where it came from.

This allows dynamic languages to expose their objects to C# in a way that feels natural to a C# programmer.

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