Question

Is accessing a bool field atomic in C#? In particular, do I need to put a lock around:

class Foo {    private bool _bar;     //... in some function on any thread (or many threads)    _bar = true;     //... same for a read    if (_bar) { ... } } 

Answer 1

Yes.

Reads and writes of the following data types are atomic: bool, char, byte, sbyte, short, ushort, uint, int, float, and reference types.

as found in C# Language Spec.

Edit: It’s probably also worthwhile understanding the volatile keyword.