C Sharp 4.0
version of the C# programming language
C# 4.0 is a version of the C# programming language that was released on April 11, 2010. Microsoft released the 4.0 runtime and development environment Visual Studio 2010. The major focus of C# 4.0 is interoperability with partially or fully dynamically typed languages and frameworks, such as the Dynamic Language Runtime and COM.
Features
The following new features were added in C# 4.0.
Dynamic member lookup
A new pseudo-type dynamic is introduced into the C# type system. It is treated as System.Object, but in addition, any member access (method call, field, property, or indexer access, or a delegate invocation) or application of an operator on a value of such type is permitted without any type checking, and its resolution is postponed until run-time. This is known as duck typing. For example:
Dynamic method calls are triggered by a value of type dynamic as any implicit or explicit parameter (and not just a receiver). For example:
Dynamic lookup is performed using three distinct mechanisms: COM IDispatch for COM objects, IDynamicMetaObjectProvider DLR interface for objects implementing that interface, and reflection for all other objects. Any C# class can therefore intercept dynamic calls on its instances by implementing IDynamicMetaObjectProvider.
In case of dynamic method and indexer calls, overload resolution happens at run-time according to the actual types of the values passed as arguments, but otherwise according to the usual C# overloading resolution rules.
“C Sharp 4.0” enters the record as version of the C# programming language. Crown Archives preserves that source wording while asking what Sharp, version and programming can confirm, complicate or overturn.
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Vocabulary and entity names are the principal evidence signals here, because they determine the precision of every later search. The source revision retrieved here is dated Jan 12, 2026. The linked authority identifier is Q5015098. The first chronological checks are 2010.
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This entry incorporates text from “C Sharp 4.0” on English Wikipedia. Contributors are listed in the page history. Text is available under the Creative Commons Attribution-ShareAlike 4.0 License. Selected authority identifiers and statements are retrieved from Wikidata under CC0; their references and qualifiers remain part of the verification path.