C＃的正确版本号是什么？什么时候出来？为什么我找不到关于C＃3.5 的答案？

这个问题主要是为了帮助那些使用不正确的版本号搜索答案的人，例如C＃3.5 。希望是任何未能找到错误版本号的答案的人都会找到这个问题，然后再使用正确的版本号进行搜索。

C# language version history:

These are the versions of C# known about at the time of this writing:

C# 1.0 released with .NET 1.0 and VS2002 (January 2002)
C# 1.2 (bizarrely enough); released with .NET 1.1 and VS2003 (April 2003). First version to call Dispose on IEnumerators which implemented IDisposable. A few other small features.
C# 2.0 released with .NET 2.0 and VS2005 (November 2005). Major new features: generics, anonymous methods, nullable types, iterator blocks
C# 3.0 released with .NET 3.5 and VS2008 (November 2007). Major new features: lambda expressions, extension methods, expression trees, anonymous types, implicit typing (var), query expressions
C# 4.0 released with .NET 4 and VS2010 (April 2010). Major new features: late binding (dynamic), delegate and interface generic variance, more COM support, named arguments, tuple data type and optional parameters
C# 5.0 released with .NET 4.5 and VS2012 (August 2012). Major features: async programming, caller info attributes. Breaking change: loop variable closure.
C# 6.0 released with .NET 4.6 and VS2015 (July 2015). Implemented by Roslyn. Features: initializers for automatically implemented properties, using directives to import static members, exception filters, element initializers, await in catch and finally, extension Add methods in collection initializers.
C# 7.0 released with .NET 4.7 and VS2017 (March 2017) Major new features: tuples, ref locals and ref return, pattern matching (including pattern-based switch statements), inline out parameter declarations, local functions, binary literals, digit separators, and arbitrary async returns.
C# 7.1 released with VS2017 v15.3 (August 2017) New features: async main, tuple member name inference, default expression, pattern matching with generics.
C# 7.2 released with VS2017 v15.5 (November 2017) New features: private protected access modifier, Span, aka interior pointer, aka stackonly struct, everything else.
C# 7.3 released with VS2017 v15.7 (May 2018). New features: enum, delegate and unmanaged generic type constraints. ref reassignment. Unsafe improvements: stackalloc initialization, unpinned indexed fixed buffers, custom fixed statements. Improved overloading resolution. Expression variables in initializers and queries. == and != defined for tuples. Auto-properties' backing fields can now be targeted by attributes.
C# 8.0 currently in preview. Expected new features: Non-nullable reference-types, IAsyncEnumerable<T> support, Ranges, and default interface methods.

In response to the OP's question:

What are the correct version numbers for C#? What came out when? Why can't I find any answers about C# 3.5?

There is no such thing as C# 3.5 - the cause of confusion here is that the C# 3.0 is present in .NET 3.5. The language and framework are versioned independently, however - as is the CLR, which is at version 2.0 for .NET 2.0 through 3.5, .NET 4 introducing CLR 4.0, service packs notwithstanding. The CLR in .NET 4.5 has various improvements, but the versioning is unclear: in some places it may be referred to as CLR 4.5 (this MSDN page used to refer to it that way, for example), but the Environment.Version property still reports 4.0.xxx.

More detailed information about the relationship between the language, runtime and framework versions is available on the C# in Depth site. This includes information about which features of C# 3.0 you can use when targeting .NET 2.0. (If anyone wants to bring all of the content into this wiki answer, they're welcome to.)

As of May 3, 2017, the C# Language Team created a history of C# versions and features on their github repo: Features Added in C# Language Versions. There is also a page that tracks upcoming and recently implemented language features.

处理 C＃的版本号时最大的问题是它与. NET Framework 的版本无关，它似乎是由于 Visual Studio 和. NET Framework 之间的同步版本。

C＃的版本实际上绑定到编译器，而不是框架。例如，在 Visual Studio 2008 中，您可以编写 C＃3.0 并以. NET Framework 2.0,3.0 和 3.5 为目标。 C＃3.0 命名法描述了代码语法的版本和支持的功能，与ANSI C89，C90，C99描述 C 的代码语法 / 功能的方式相同。

看看Mono ，你会发现 Mono 2.0（主要是从 ECMA 规范实现的. NET Framework 2.0 版本）支持 C＃3.0 语法和功能。

这与大多数答案相同，但是为了方便而制表，并且它具有 Visual Studio 和. NET 版本以实现完整性。

╔════════════╦════════════╦══════════════╦═════════════╦══════════════╗
║ 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   ║
╚════════════╩════════════╩══════════════╩═════════════╩══════════════╝

注意：.NET 开发现在几乎与 VS 无关，每个版本之间没有相关性。有关更多信息，请参阅： https ： //docs.microsoft.com/en-us/dotnet/framework/migration-guide/versions-and-dependencies 。