问题
In C# 4, the behavior of types without the beforefieldinit flag was changed, so now a type initializer can call before first use of any static field of the class.
My questions are why has the C#/.NET team changed that behavior? What is the main reason? Can you show any practical example where this change makes any sense?
回答1:
The behaviour has always been within the bounds of what's documented - it's just that it changed from being eager to lazy in .NET 4.
I suspect the JIT team managed to find a way to make it lazy without a performance penalty... or possibly it helps performance somewhere else. This is likely to only be one such change in behaviour within the .NET 4 CLR vs the .NET 2 CLR... it happens that I noticed it, but I doubt that many other people did. I think it's entirely reasonable for the JIT team to adjust things as they see fit, within the documented guarantees.
Ultimately, if this makes your code fail, you've got a bug already.
来源：https://stackoverflow.com/questions/6729841/why-did-the-beforefieldinit-behavior-change-in-net-4