In the course of its development, the C# language has gone through several versions:
Version CLR[29] Language specification Date .NET Framework Visual Studio
ECMA ISO/IEC Microsoft
C# 1.0 1.0 December 2002 April 2003 January 2002 January 2002 .NET Framework 1.0 Visual Studio .NET 2002
C# 1.2 1.1 October 2003 April 2003 .NET Framework 1.1 Visual Studio .NET 2003
C# 2.0 2.0 June 2006 September 2006 September 2005[A] November 2005 .NET Framework 2.0 Visual Studio 2005
C# 3.0 2.02.0 SP1 None[B] August 2007 November 2007 .NET Framework 2.0 (Except LINQ/Query Extensions)[30].NET Framework 3.0 (Except LINQ/Query Extensions)[30].NET Framework 3.5 Visual Studio 2008Visual Studio 2010
C# 4.0 4.0[C] April 2010 April 2010 .NET Framework 4 Visual Studio 2010
C# 5.0 4.5[D] June 2013 August 2012 .NET Framework 4.5 Visual Studio 2013
A The Microsoft C# 2.0 specification document only contains the new 2.0 features. For older features use the 1.2 specification above.
B No ECMA or ISO/IEC specifications exist for C# 3.0, 4.0 or 5.0.
C There was no CLR version 3.0.
D CLR documentation refers to as 4.5 but Environment.Version points to 4.0.[31]
Summary of versions
C# 2.0 C# 3.0 C# 4.0 C# 5.0 [32] Future
Featuresadded GenericsPartial typesAnonymous methodsIteratorsNullable typesPrivate setters (properties)Method group conversions (delegates)Covariance and Contra-varianceStatic classes Implicitly typed local variablesObject and collection initializersAuto-Implemented propertiesAnonymous typesExtension methodsQuery expressionsLambda expressionsExpression treesPartial Methods Dynamic bindingNamed and optional argumentsGeneric co- and contravarianceEmbedded interop types ("NoPIA") Asynchronous methodsCaller info attributes C# 5.0Compiler-as-a-service (Roslyn)C# 6.0Import type members into namespaceSuccinct syntax for primary constructorsReadonly propertiesProperty expressions (property lambdas)Method expressionsParameter arrays for IEnumerable interfacesSuccinct null checkingMultiple return valuesConstructor type inference