Question

I’d like to know how you know when to lock an entire type

lock (typeof(MyClass))
{
...
}

or an instance

lock (this)
{
...
}

or an object

lock (this._lockObj)
{
...
}

I am asking this because I have a static class that is a simple Wrapper for Enterprise Library 5 and is accessed by multiple components from possibly different threads. The WriteLog() method is locked. I use the type to lock.

Answer 1

First rule. Lock using object that is not accessible from outside of class. That’s why this and various typeofs are bad idea. Outer code can interfere with your locks. Then question is what scope of lock is it. If it is static then use static field otherwise use instance field.

To pick correct lock object you should you identify groups of code that are mutually exclusive. So if you have 4 methods that are exclusive in pairs like A and B , C and D you should have 2 differenet lock objects, not 1.