Question

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.

Answer 1

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++.