Is a readonly field in C# thread safe?

Question

Is a readonly field in C# thread safe?

public class Foo
{
  private readonly int _someField;

  public Foo()
  {
    _someField = 0;
  }

  publ         


        

Answer 1

Yes - your code doesn't expose this within either constructor, so no other code can "see" the object before it's been fully constructed. The .NET memory model (as of .NET 2) includes a write barrier at the end of every constructor (IIRC - search Joe Duffy's blog posts for more details) so there's no risk of another thread seeing a "stale" value, as far as I'm aware.

I'd personally still usually use a property instead, as a way of separating implementation from API, but from a thread-safety point of view it's fine.