C# doesn't allow locking on a null value. I suppose I could check whether the value is null or not before I lock it, but because I haven't locked it another thread could come along and make the value null! How can I avoid this race condition?
Lock on a value that is never null, e.g.
Object _lockOnMe = new Object();
Object _iMightBeNull;
public void DoSomeKungFu() {
if (_iMightBeNull == null) {
lock (_lockOnMe) {
if (_iMightBeNull == null) {
_iMightBeNull = ... whatever ...;
}
}
}
}
Also be careful to avoid this interesting race condition with double-checked locking: Memory Model Guarantees in Double-checked Locking