What are the correct version numbers for C#? What came out when? Why can't I find any answers about C# 3.5?
This question is primarily to aid those who are searching for an answer using an incorrect version number, e.g. C# 3.5. The hope is that anyone failing to find an answer with the wrong version number will find this question and then search again with the right version number.
This question is related to
c#
.net
visual-studio
.net-framework-version
compiler-version
The answer is
Version .NET Framework Visual Studio Important Features
C# 1.0 .NET Framework 1.0/1.1 Visual Studio .NET 2002
Basic features
C# 2.0 .NET Framework 2.0 Visual Studio 2005
Generics
Partial types
Anonymous methods
Iterators
Nullable types
Private setters (properties)
Method group conversions (delegates)
Covariance and Contra-variance
Static classes
C# 3.0 .NET Framework 3.0\3.5 Visual Studio 2008
Implicitly typed local variables
Object and collection initializers
Auto-Implemented properties
Anonymous types
Extension methods
Query expressions
Lambda expressions
Expression trees
Partial Methods
C# 4.0 .NET Framework 4.0 Visual Studio 2010
Dynamic binding (late binding)
Named and optional arguments
Generic co- and contravariance
Embedded interop types
C# 5.0 .NET Framework 4.5 Visual Studio 2012/2013
Async features
Caller information
C# 6.0 .NET Framework 4.6 Visual Studio 2013/2015
Expression Bodied Methods
Auto-property initializer
nameof Expression
Primary constructor
Await in catch block
Exception Filter
String Interpolation
C# 7.0 .NET Core 2.0 Visual Studio 2017
out variables
Tuples
Discards
Pattern Matching
Local functions
Generalized async return types
Numeric literal syntax improvements
C# 8.0 .NET Core 3.0 Visual Studio 2019
Readonly members
Default interface methods
Pattern matching enhancements:
Switch expressions
Property patterns
Tuple patterns
Positional patterns
Using declarations
Static local functions
Disposable ref structs
Nullable reference types
Asynchronous streams
Asynchronous disposable
Indices and ranges
Null-coalescing assignment
Unmanaged constructed types
Stackalloc in nested expressions
Enhancement of interpolated verbatim strings
This is the same as most answers here, but tabularized for ease, and it has Visual Studio and .NET versions for completeness.
| C# version | VS version | .NET version | CLR version | Release date |
|---|---|---|---|---|
| 1.0 | 2002 | 1.0 | 1.0 | Feb 2002 |
| 1.2 | 2003 | 1.1 | 1.1 | Apr 2003 |
| 2.0 | 2005 | 2.0 | 2.0 | Nov 2005 |
| 3.0 | 2.0 | Nov 2006 | ||
| 3.0 | 2008 | 3.5 | 2.0 | Nov 2007 |
| 4.0 | 2010 | 4.0 | 4 | Apr 2010 |
| 5.0 | 2012 | 4.5 | 4 | Aug 2012 |
| 5.0 | 2013 | 4.5.1 | 4 | Oct 2013 |
| 4.5.2 | 4 | May 2014 | ||
| 6.0 | 2015 | 4.6 | 4 | Jul 2015 |
| 4.6.1 | 4 | Nov 2015 | ||
| 4.6.2 | 4 | Aug 2016 | ||
| 7.0 | 2017 | Mar 2017 | ||
| 4.7 | 4 | May 2017 | ||
| 7.1 | 2017(v15.3) | Aug 2017 | ||
| 4.7.1 | 4 | Oct 2017 | ||
| 7.2 | 2017(v15.5) | Dec 2017 | ||
| 4.7.2 | 4 | Apr 2018 | ||
| 7.3 | 2017(v15.7) | May 2018 | ||
| 8.0 | 2019 | 4.8 | 4 | Apr 2019 |
| 9.0 | 2019(v16.8) | 5.0^ | ^^ | Nov 2020 |
^ - .NET 5.0 is not a newer version of .NET framework but .NET Core 3. Starting from .NET 5.0, there are no newer versions of .NET full framework.
^^ - There are no separate CLR (CoreCLR) versions for .NET Core. Whatever is the .NET Core version is the CoreCLR version. So not mentioning it.
Note: .NET development is pretty much independent of VS these days, there is no correlation between versions of each.
Refer to ".NET Framework versions and dependencies" for more.
C# Version History:
C# is a simple and powerful object-oriented programming language developed by Microsoft.
C# has evolved much since its first release in 2002. C# was introduced with .NET Framework 1.0.
The following table lists important features introduced in each version of C#.
And the latest version of C# is available in C# Versions.
1: 
C# 8.0 is the latest version of c#.it is supported only on .NET Core 3.x and newer versions. Many of the newest features require library and runtime features introduced in .NET Core 3.x
The following table lists the target framework with version and their default C# version.
C# 1.0 with Visual Studio.NET
C# 2.0 with Visual Studio 2005
C# 3.0 with Visual Studio 2008
C# 4.0 with Visual Studio 2010
C# 5.0 with Visual Studio 2012
C# 6.0 with Visual Studio 2015
C# 7.0 with Visual Studio 2017
C# 8.0 with Visual Studio 2019
This is the same as most answers here, but tabularized for ease, and it has Visual Studio and .NET versions for completeness.
| C# version | VS version | .NET version | CLR version | Release date |
|---|---|---|---|---|
| 1.0 | 2002 | 1.0 | 1.0 | Feb 2002 |
| 1.2 | 2003 | 1.1 | 1.1 | Apr 2003 |
| 2.0 | 2005 | 2.0 | 2.0 | Nov 2005 |
| 3.0 | 2.0 | Nov 2006 | ||
| 3.0 | 2008 | 3.5 | 2.0 | Nov 2007 |
| 4.0 | 2010 | 4.0 | 4 | Apr 2010 |
| 5.0 | 2012 | 4.5 | 4 | Aug 2012 |
| 5.0 | 2013 | 4.5.1 | 4 | Oct 2013 |
| 4.5.2 | 4 | May 2014 | ||
| 6.0 | 2015 | 4.6 | 4 | Jul 2015 |
| 4.6.1 | 4 | Nov 2015 | ||
| 4.6.2 | 4 | Aug 2016 | ||
| 7.0 | 2017 | Mar 2017 | ||
| 4.7 | 4 | May 2017 | ||
| 7.1 | 2017(v15.3) | Aug 2017 | ||
| 4.7.1 | 4 | Oct 2017 | ||
| 7.2 | 2017(v15.5) | Dec 2017 | ||
| 4.7.2 | 4 | Apr 2018 | ||
| 7.3 | 2017(v15.7) | May 2018 | ||
| 8.0 | 2019 | 4.8 | 4 | Apr 2019 |
| 9.0 | 2019(v16.8) | 5.0^ | ^^ | Nov 2020 |
^ - .NET 5.0 is not a newer version of .NET framework but .NET Core 3. Starting from .NET 5.0, there are no newer versions of .NET full framework.
^^ - There are no separate CLR (CoreCLR) versions for .NET Core. Whatever is the .NET Core version is the CoreCLR version. So not mentioning it.
Note: .NET development is pretty much independent of VS these days, there is no correlation between versions of each.
Refer to ".NET Framework versions and dependencies" for more.
Version .NET Framework Visual Studio Important Features
C# 1.0 .NET Framework 1.0/1.1 Visual Studio .NET 2002
Basic features
C# 2.0 .NET Framework 2.0 Visual Studio 2005
Generics
Partial types
Anonymous methods
Iterators
Nullable types
Private setters (properties)
Method group conversions (delegates)
Covariance and Contra-variance
Static classes
C# 3.0 .NET Framework 3.0\3.5 Visual Studio 2008
Implicitly typed local variables
Object and collection initializers
Auto-Implemented properties
Anonymous types
Extension methods
Query expressions
Lambda expressions
Expression trees
Partial Methods
C# 4.0 .NET Framework 4.0 Visual Studio 2010
Dynamic binding (late binding)
Named and optional arguments
Generic co- and contravariance
Embedded interop types
C# 5.0 .NET Framework 4.5 Visual Studio 2012/2013
Async features
Caller information
C# 6.0 .NET Framework 4.6 Visual Studio 2013/2015
Expression Bodied Methods
Auto-property initializer
nameof Expression
Primary constructor
Await in catch block
Exception Filter
String Interpolation
C# 7.0 .NET Core 2.0 Visual Studio 2017
out variables
Tuples
Discards
Pattern Matching
Local functions
Generalized async return types
Numeric literal syntax improvements
C# 8.0 .NET Core 3.0 Visual Studio 2019
Readonly members
Default interface methods
Pattern matching enhancements:
Switch expressions
Property patterns
Tuple patterns
Positional patterns
Using declarations
Static local functions
Disposable ref structs
Nullable reference types
Asynchronous streams
Asynchronous disposable
Indices and ranges
Null-coalescing assignment
Unmanaged constructed types
Stackalloc in nested expressions
Enhancement of interpolated verbatim strings
The biggest problem when dealing with C#'s version numbers is the fact that it is not tied to a version of the .NET Framework, which it appears to be due to the synchronized releases between Visual Studio and the .NET Framework.
The version of C# is actually bound to the compiler, not the framework. For instance, in Visual Studio 2008 you can write C# 3.0 and target .NET Framework 2.0, 3.0 and 3.5. The C# 3.0 nomenclature describes the version of the code syntax and supported features in the same way that ANSI C89, C90, C99 describe the code syntax/features for C.
Take a look at Mono, and you will see that Mono 2.0 (mostly implemented version 2.0 of the .NET Framework from the ECMA specifications) supports the C# 3.0 syntax and features.
I've summarised most of the versions in this table. The only ones missing should be ASP.NET Core versions. I've also added different versions of ASP.NET MVC.
Note that ASP.NET 5 has been rebranded as ASP.NET Core 1.0 and ASP.NET MVC 6 has been rebranded as ASP.NET Core MVC 1.0.0. I believe this change occurred sometime around Jan 2016.
I have included the release date of ASP.NET 5 RC1 in the table, but I've yet to include ASP.NET core 1.0 and other core versions, because I couldn't find the exact release dates. You can read more about the release dates regarding ASP.NET Core here: When is ASP.NET Core 1.0 (ASP.NET 5 / vNext) scheduled for release?
VERSION_____LANGUAGE SPECIFICATION______MICROSOFT COMPILER
C# 1.0/1.2____December 2001?/2003?___________January 2002?
C# 2.0_______September 2005________________November 2005?
C# 3.0_______May 2006_____________________November 2006?
C# 4.0_______March 2009 (draft)______________April 2010?
C# 5.0; released with .NET 4.5 in August 2012
C# 6.0; released with .NET 4.6 2015
C# 7.0; released with .NET 4.7 2017
C# 8.0; released with .NET 4.8 2019
You can check the latest C# versions here
C# 1.0 with Visual Studio.NET
C# 2.0 with Visual Studio 2005
C# 3.0 with Visual Studio 2008
C# 4.0 with Visual Studio 2010
C# 5.0 with Visual Studio 2012
C# 6.0 with Visual Studio 2015
C# 7.0 with Visual Studio 2017
C# 8.0 with Visual Studio 2019
VERSION_____LANGUAGE SPECIFICATION______MICROSOFT COMPILER
C# 1.0/1.2____December 2001?/2003?___________January 2002?
C# 2.0_______September 2005________________November 2005?
C# 3.0_______May 2006_____________________November 2006?
C# 4.0_______March 2009 (draft)______________April 2010?
C# 5.0; released with .NET 4.5 in August 2012
C# 6.0; released with .NET 4.6 2015
C# 7.0; released with .NET 4.7 2017
C# 8.0; released with .NET 4.8 2019
C# 1.0 - Visual Studio .NET 2002
Classes
Structs
Interfaces
Events
Properties
Delegates
Expressions
Statements
Attributes
Literals
C# 1.2 - Visual Studio .NET 2003
Dispose in foreach
foreach over string specialization
C# 2 - Visual Studio 2005
Generics
Partial types
Anonymous methods
Iterators
Nullable types
Getter/setter separate accessibility
Method group conversions (delegates)
Static classes
Delegate inference
C# 3 - Visual Studio 2008
Implicitly typed local variables
Object and collection initializers
Auto-Implemented properties
Anonymous types
Extension methods
Query expressions
Lambda expression
Expression trees
Partial methods
C# 4 - Visual Studio 2010
Dynamic binding
Named and optional arguments
Co- and Contra-variance for generic delegates and interfaces
Embedded interop types ("NoPIA")
C# 5 - Visual Studio 2012
Asynchronous methods
Caller info attributes
C# 6 - Visual Studio 2015
Draft Specification online
Compiler-as-a-service (Roslyn)
Import of static type members into namespace
Exception filters
Await in catch/finally blocks
Auto property initializers
Default values for getter-only properties
Expression-bodied members
Null propagator (null-conditional operator, succinct null checking)
String interpolation
nameof operator
Dictionary initializer
C# 7.0 - Visual Studio 2017
Out variables
Pattern matching
Tuples
Deconstruction
Discards
Local Functions
Binary Literals
Digit Separators
Ref returns and locals
Generalized async return types
More expression-bodied members
Throw expressions
C# 7.1 - Visual Studio 2017 version 15.3
Async main
Default expressions
Reference assemblies
Inferred tuple element names
Pattern-matching with generics
C# 7.2 - Visual Studio 2017 version 15.5
Span and ref-like types
In parameters and readonly references
Ref conditional
Non-trailing named arguments
Private protected accessibility
Digit separator after base specifier
C# 7.3 - Visual Studio 2017 version 15.7
System.Enum, System.Delegate and unmanaged constraints.
Ref local re-assignment: Ref locals and ref parameters can now be reassigned with the ref assignment operator (= ref).
Stackalloc initializers: Stack-allocated arrays can now be initialized, e.g. Span<int> x = stackalloc[] { 1, 2, 3 };.
Indexing movable fixed buffers: Fixed buffers can be indexed into without first being pinned.
Custom fixed statement: Types that implement a suitable GetPinnableReference can be used in a fixed statement.
Improved overload candidates: Some overload resolution candidates can be ruled out early, thus reducing ambiguities.
Expression variables in initializers and queries: Expression variables like out var and pattern variables are allowed in field initializers, constructor initializers and LINQ queries.
Tuple comparison: Tuples can now be compared with == and !=.
Attributes on backing fields: Allows [field: …] attributes on an auto-implemented property to target its backing field.
C# 8.0 - .NET Core 3.0 and Visual Studio 2019 version 16.3
Nullable reference types: express nullability intent on reference types with ?, notnull constraint and annotations attributes in APIs, the compiler will use those to try and detect possible null values being dereferenced or passed to unsuitable APIs.
Default interface members: interfaces can now have members with default implementations, as well as static/private/protected/internal members except for state (ie. no fields).
Recursive patterns: positional and property patterns allow testing deeper into an object, and switch expressions allow for testing multiple patterns and producing corresponding results in a compact fashion.
Async streams: await foreach and await using allow for asynchronous enumeration and disposal of IAsyncEnumerable<T> collections and IAsyncDisposable resources, and async-iterator methods allow convenient implementation of such asynchronous streams.
Enhanced using: a using declaration is added with an implicit scope and using statements and declarations allow disposal of ref structs using a pattern.
Ranges and indexes: the i..j syntax allows constructing System.Range instances, the ^k syntax allows constructing System.Index instances, and those can be used to index/slice collections.
Null-coalescing assignment: ??= allows conditionally assigning when the value is null.
Static local functions: local functions modified with static cannot capture this or local variables, and local function parameters now shadow locals in parent scopes.
Unmanaged generic structs: generic struct types that only have unmanaged fields are now considered unmanaged (ie. they satisfy the unmanaged constraint).
Readonly members: individual members can now be marked as readonly to indicate and enforce that they do not modify instance state.
Stackalloc in nested contexts: stackalloc expressions are now allowed in more expression contexts.
Alternative interpolated verbatim strings: @$"..." strings are recognized as interpolated verbatim strings just like $@"...".
Obsolete on property accessors: property accessors can now be individually marked as obsolete.
Permit t is null on unconstrained type parameter
[source] : https://github.com/dotnet/csharplang/blob/master/Language-Version-History.md
The most recent version is 9.0, which was released in 2020 in .NET 5.0 and included in Visual Studio 2019 version 16.8. Mono is a free and open-source project to develop a cross-platform compiler and runtime environment (i.e. virtual machine) for the language.
C# Version History:
C# is a simple and powerful object-oriented programming language developed by Microsoft.
C# has evolved much since its first release in 2002. C# was introduced with .NET Framework 1.0.
The following table lists important features introduced in each version of C#.
And the latest version of C# is available in C# Versions.
1:
I've summarised most of the versions in this table. The only ones missing should be ASP.NET Core versions. I've also added different versions of ASP.NET MVC.
Note that ASP.NET 5 has been rebranded as ASP.NET Core 1.0 and ASP.NET MVC 6 has been rebranded as ASP.NET Core MVC 1.0.0. I believe this change occurred sometime around Jan 2016.
I have included the release date of ASP.NET 5 RC1 in the table, but I've yet to include ASP.NET core 1.0 and other core versions, because I couldn't find the exact release dates. You can read more about the release dates regarding ASP.NET Core here: When is ASP.NET Core 1.0 (ASP.NET 5 / vNext) scheduled for release?
The most recent version is 9.0, which was released in 2020 in .NET 5.0 and included in Visual Studio 2019 version 16.8. Mono is a free and open-source project to develop a cross-platform compiler and runtime environment (i.e. virtual machine) for the language.
The biggest problem when dealing with C#'s version numbers is the fact that it is not tied to a version of the .NET Framework, which it appears to be due to the synchronized releases between Visual Studio and the .NET Framework.
The version of C# is actually bound to the compiler, not the framework. For instance, in Visual Studio 2008 you can write C# 3.0 and target .NET Framework 2.0, 3.0 and 3.5. The C# 3.0 nomenclature describes the version of the code syntax and supported features in the same way that ANSI C89, C90, C99 describe the code syntax/features for C.
Take a look at Mono, and you will see that Mono 2.0 (mostly implemented version 2.0 of the .NET Framework from the ECMA specifications) supports the C# 3.0 syntax and features.
C# 1.0 - Visual Studio .NET 2002
Classes
Structs
Interfaces
Events
Properties
Delegates
Expressions
Statements
Attributes
Literals
C# 1.2 - Visual Studio .NET 2003
Dispose in foreach
foreach over string specialization
C# 2 - Visual Studio 2005
Generics
Partial types
Anonymous methods
Iterators
Nullable types
Getter/setter separate accessibility
Method group conversions (delegates)
Static classes
Delegate inference
C# 3 - Visual Studio 2008
Implicitly typed local variables
Object and collection initializers
Auto-Implemented properties
Anonymous types
Extension methods
Query expressions
Lambda expression
Expression trees
Partial methods
C# 4 - Visual Studio 2010
Dynamic binding
Named and optional arguments
Co- and Contra-variance for generic delegates and interfaces
Embedded interop types ("NoPIA")
C# 5 - Visual Studio 2012
Asynchronous methods
Caller info attributes
C# 6 - Visual Studio 2015
Draft Specification online
Compiler-as-a-service (Roslyn)
Import of static type members into namespace
Exception filters
Await in catch/finally blocks
Auto property initializers
Default values for getter-only properties
Expression-bodied members
Null propagator (null-conditional operator, succinct null checking)
String interpolation
nameof operator
Dictionary initializer
C# 7.0 - Visual Studio 2017
Out variables
Pattern matching
Tuples
Deconstruction
Discards
Local Functions
Binary Literals
Digit Separators
Ref returns and locals
Generalized async return types
More expression-bodied members
Throw expressions
C# 7.1 - Visual Studio 2017 version 15.3
Async main
Default expressions
Reference assemblies
Inferred tuple element names
Pattern-matching with generics
C# 7.2 - Visual Studio 2017 version 15.5
Span and ref-like types
In parameters and readonly references
Ref conditional
Non-trailing named arguments
Private protected accessibility
Digit separator after base specifier
C# 7.3 - Visual Studio 2017 version 15.7
System.Enum, System.Delegate and unmanaged constraints.
Ref local re-assignment: Ref locals and ref parameters can now be reassigned with the ref assignment operator (= ref).
Stackalloc initializers: Stack-allocated arrays can now be initialized, e.g. Span<int> x = stackalloc[] { 1, 2, 3 };.
Indexing movable fixed buffers: Fixed buffers can be indexed into without first being pinned.
Custom fixed statement: Types that implement a suitable GetPinnableReference can be used in a fixed statement.
Improved overload candidates: Some overload resolution candidates can be ruled out early, thus reducing ambiguities.
Expression variables in initializers and queries: Expression variables like out var and pattern variables are allowed in field initializers, constructor initializers and LINQ queries.
Tuple comparison: Tuples can now be compared with == and !=.
Attributes on backing fields: Allows [field: …] attributes on an auto-implemented property to target its backing field.
C# 8.0 - .NET Core 3.0 and Visual Studio 2019 version 16.3
Nullable reference types: express nullability intent on reference types with ?, notnull constraint and annotations attributes in APIs, the compiler will use those to try and detect possible null values being dereferenced or passed to unsuitable APIs.
Default interface members: interfaces can now have members with default implementations, as well as static/private/protected/internal members except for state (ie. no fields).
Recursive patterns: positional and property patterns allow testing deeper into an object, and switch expressions allow for testing multiple patterns and producing corresponding results in a compact fashion.
Async streams: await foreach and await using allow for asynchronous enumeration and disposal of IAsyncEnumerable<T> collections and IAsyncDisposable resources, and async-iterator methods allow convenient implementation of such asynchronous streams.
Enhanced using: a using declaration is added with an implicit scope and using statements and declarations allow disposal of ref structs using a pattern.
Ranges and indexes: the i..j syntax allows constructing System.Range instances, the ^k syntax allows constructing System.Index instances, and those can be used to index/slice collections.
Null-coalescing assignment: ??= allows conditionally assigning when the value is null.
Static local functions: local functions modified with static cannot capture this or local variables, and local function parameters now shadow locals in parent scopes.
Unmanaged generic structs: generic struct types that only have unmanaged fields are now considered unmanaged (ie. they satisfy the unmanaged constraint).
Readonly members: individual members can now be marked as readonly to indicate and enforce that they do not modify instance state.
Stackalloc in nested contexts: stackalloc expressions are now allowed in more expression contexts.
Alternative interpolated verbatim strings: @$"..." strings are recognized as interpolated verbatim strings just like $@"...".
Obsolete on property accessors: property accessors can now be individually marked as obsolete.
Permit t is null on unconstrained type parameter
[source] : https://github.com/dotnet/csharplang/blob/master/Language-Version-History.md
You can check the latest C# versions here
The biggest problem when dealing with C#'s version numbers is the fact that it is not tied to a version of the .NET Framework, which it appears to be due to the synchronized releases between Visual Studio and the .NET Framework.
The version of C# is actually bound to the compiler, not the framework. For instance, in Visual Studio 2008 you can write C# 3.0 and target .NET Framework 2.0, 3.0 and 3.5. The C# 3.0 nomenclature describes the version of the code syntax and supported features in the same way that ANSI C89, C90, C99 describe the code syntax/features for C.
Take a look at Mono, and you will see that Mono 2.0 (mostly implemented version 2.0 of the .NET Framework from the ECMA specifications) supports the C# 3.0 syntax and features.
C# 8.0 is the latest version of c#.it is supported only on .NET Core 3.x and newer versions. Many of the newest features require library and runtime features introduced in .NET Core 3.x
The following table lists the target framework with version and their default C# version.
Comparing the MSDN articles "What's New in the C# 2.0 Language and Compiler" and "What's New in Visual C# 2005", it is possible to deduce that "C# major_version.minor_version" is coined according to the compiler's version numbering.
There is C# 1.2 corresponding to .NET 1.1 and VS 2003 and also named as Visual C# .NET 2003.
But further on Microsoft stopped to increment the minor version (after the dot) numbers or to have them other than zero, 0. Though it should be noted that C# corresponding to .NET 3.5 is named in msdn.microsoft.com as "Visual C# 2008 Service Pack 1".
There are two parallel namings: By major .NET/compiler version numbering and by Visual Studio numbering.
C# 2.0 is a synonym for Visual C# 2005
C# 3.0 corresponds (or, more correctly, can target) to:
- .NET 2.0 <==> Visual C# 2005
- .NET3.0 <==> Visual C# 2008
- .NET 3.5 <==> Visual C# 2008 Service Pack 1
The biggest problem when dealing with C#'s version numbers is the fact that it is not tied to a version of the .NET Framework, which it appears to be due to the synchronized releases between Visual Studio and the .NET Framework.
The version of C# is actually bound to the compiler, not the framework. For instance, in Visual Studio 2008 you can write C# 3.0 and target .NET Framework 2.0, 3.0 and 3.5. The C# 3.0 nomenclature describes the version of the code syntax and supported features in the same way that ANSI C89, C90, C99 describe the code syntax/features for C.
Take a look at Mono, and you will see that Mono 2.0 (mostly implemented version 2.0 of the .NET Framework from the ECMA specifications) supports the C# 3.0 syntax and features.
Comparing the MSDN articles "What's New in the C# 2.0 Language and Compiler" and "What's New in Visual C# 2005", it is possible to deduce that "C# major_version.minor_version" is coined according to the compiler's version numbering.
There is C# 1.2 corresponding to .NET 1.1 and VS 2003 and also named as Visual C# .NET 2003.
But further on Microsoft stopped to increment the minor version (after the dot) numbers or to have them other than zero, 0. Though it should be noted that C# corresponding to .NET 3.5 is named in msdn.microsoft.com as "Visual C# 2008 Service Pack 1".
There are two parallel namings: By major .NET/compiler version numbering and by Visual Studio numbering.
C# 2.0 is a synonym for Visual C# 2005
C# 3.0 corresponds (or, more correctly, can target) to:
- .NET 2.0 <==> Visual C# 2005
- .NET3.0 <==> Visual C# 2008
- .NET 3.5 <==> Visual C# 2008 Service Pack 1
Source: Stackoverflow.com