How does StringBuilder work internally in C#?

Question

How does StringBuilder work?

What does it do internally? Does it use unsafe code? And why is it so fast (compared to the + opera

Answer 1

The Microsoft CLR does do some operations with internal call (not quite the same as unsafe code). The biggest performance benefit over a bunch of + concatenated strings is that it writes to a char[] and doesn't create as many intermediate strings. When you call ToString (), it builds a completed, immutable string from your contents.