如何编译C＃与特定语言版本

本文介绍了如何编译C＃与特定语言版本的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

比方说，我想演示，某人的foreach在C＃4.0和5.0之间的差异。

Let's say I want to demo to someone about the differences between foreach in C# 4.0 and 5.0.

所以，我写我的代码片段：

So I write up my code snippet:

public static void Main() { string[] fruits = { "Apple", "Banana", "Cantelope" }; var actions = new List<Action>(); foreach (var fruit in fruits) { actions.Add(() => Console.WriteLine(fruit)); } foreach(var a in actions) { a(); } }

但无论我怎么编译它，它始终工作因为它在5.0 * 。我已经试过了的csproj文件中设置语言版本（建设 - >高级 - >语言版本），我已经试过只是构建它的命令行：

But no matter how I compile it, it always works as it does in 5.0*. I've tried setting the language version in the csproj file (Build -> Advanced -> Language Version) and I've tried just building it on the command line:

csc myProgram.cs /langversion:4

我不能得到它的工作的老的方式。任何帮助吗？奖励积分，如果你能告诉我怎么做它的命令行和Visual Studio上都。

I can't get it to work the "old" way. Any help? Bonus points if you can tell me how to do it on both the command line and Visual Studio.

*对于任何人谁不知道，在C＃。 < = 4.0，这将打印 Cantelope Cantelope Cantelope ，而在C＃5.0+的那样（更直观地）打印苹果香蕉Cantelope 。 这里有一个链接和的here's另一个。

* For anyone who doesn't know, in C#. <= 4.0 this would print Cantelope Cantelope Cantelope, while in C# 5.0+ it would (more intuitively) print Apple Banana Cantelope. Here's a link, and here's another.

推荐答案

的目的 / langversion 仅使编译器接受特定的语言结构。它不影响编译器的实际行为。

The purpose of the /langversion is only to make the compiler accept specific language constructs. It does not affect the actual behaviour of the compiler.

文档指出：

使编译器只接受包含语法在选择C＃语言规范。

Causes the compiler to accept only syntax that is included in the chosen C# language specification.

和

由于C＃编译器的每个版本包含扩展的语言规范，/ langversion不给你的编译器的早期版本的等效功能。

Because each version of the C# compiler contains extensions to the language specification, /langversion does not give you the equivalent functionality of an earlier version of the compiler.

所以要表现出不同的行为，你将不得不使用不同的CSC.EXE，用正确的框架版本安装。

So to demonstrate the different behaviour, you will have to use a different csc.exe, installed with the right framework versions.

C:\Windows\Microsoft.NET\Framework\v3.5>csc /out:c:\temp\foo-35.exe c:\temp\foo.cs Microsoft (R) Visual C# 2008 Compiler version 3.5.30729.7903 for Microsoft (R) .NET Framework version 3.5 Copyright (C) Microsoft Corporation. All rights reserved. C:\Windows\Microsoft.NET\Framework\v3.5>c:\temp\foo-35.exe Cantelope Cantelope Cantelope