C＃4.0向下兼容C＃2.0？ [英] Is C# 4.0 backward compatible to C# 2.0?

问题描述

我可以知道C＃4.0和C＃2.0之间有什么区别吗？是C＃4.0向下兼容C＃2.0？

我可以说C＃4.0是C＃2.0的超集（就像C ++对C）

感谢。

解决方案

与以前的版本兼容，但有几个突变。对于大多数普通代码，您不会注意到这些突变的更改。

对于C＃4中的新功能，您可以查看维基百科文章，其中有很多例子。重点是：

• 动态成员查询


• 协变和逆变通用类型参数


• 使用COM时可选的参数关键字


• 可选参数和命名参数


• 索引属性

还要记住，在中间有另一个版本 - C＃3.0。这里最重要的补充之一是LINQ和所有的功能添加，使其成为可能。 C＃2.0和3.0之间的差异远远大于C＃3.0和4.0之间的差异。

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所有有效的C代码是有效的C ++，如你暗示在你的问题。请参见此处：

在严格的数学意义上，C不是C ++的子集。有些程序是有效的C但不是有效的C ++，甚至几种方法编写代码在C和C ++中有不同的含义。

May I know what is the difference between C# 4.0 and C# 2.0? Is C# 4.0 backward compatible to C# 2.0?

Can I say that C# 4.0 is a superset of C# 2.0 (just like what C++ is to C)?

Thanks.

解决方案

C# 4.0 is nearly backwards compatible with previous versions but there are a few breaking changes. For most ordinary code you won't notice these breaking changes.

For the new features in C# 4 you can check out the Wikipedia article which has quite a good summary with examples. The key points are:

• Dynamic member lookup
• Covariant and contravariant generic type parameters
• Optional ref keyword when using COM
• Optional parameters and named arguments
• Indexed properties

Also remember that there was another version in between - C# 3.0. One of the most important additions here is LINQ and all the features added to make it possible. The difference between C# 2.0 and 3.0 is much greater than the difference between C# 3.0 and 4.0.

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By the way, not all valid C code is valid C++ as you implied in your question. See here:

In the strict mathematical sense, C isn't a subset of C++. There are programs that are valid C but not valid C++ and even a few ways of writing code that has a different meaning in C and C++.

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