Monitor vs lock

Question

When is it appropriate to use either the Monitor class or the lock keyword for thread safety in C#?

EDIT: It seems from th

Answer 1

Eric Lippert talks about this in his blog: Locks and exceptions do not mix

The equivalent code differs between C# 4.0 and earlier versions.

---

In C# 4.0 it is:

bool lockWasTaken = false;
var temp = obj;
try
{
    Monitor.Enter(temp, ref lockWasTaken);
    { body }
}
finally
{
    if (lockWasTaken) Monitor.Exit(temp);
}

It relies on Monitor.Enter atomically setting the flag when the lock is taken.

---

And earlier it was:

var temp = obj;
Monitor.Enter(temp);
try
{
   body
}
finally
{
    Monitor.Exit(temp);
}

This relies on no exception being thrown between Monitor.Enter and the try. I think in debug code this condition was violated because the compiler inserted a NOP between them and thus made thread abortion between those possible.