最初的 C# 编译器不是用 C# 编写的，而是用 C 和 C++ 编写的.新的 Roslyn 编译器是用 C# 编写的，但最初是使用旧编译器编译的.新编译器完成后，就可以编译自己的源代码:这称为 bootstrapping.

The original C# compiler wasn't written in C#, it was in C and C++. The new Roslyn compiler was written in C#, but was initially compiled with the old compiler. Once the new compiler was done, it was able to compile its own source code: this is called bootstrapping.