Why doesn't C# allow a null value to be locked?

Question

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 c

Answer 1

There are two issues here:

First, don't lock on a null object. It doesn't make sense as how can two objects, both null, be differentiated?

Second, to safely initialise a variable in a multithreaded environment, use the double-checked locking pattern:

if (o == null) {
    lock (lockObj) {
        if (o == null) {
            o = new Object();
        }
    }
}

This will ensure that another thread has not already initialised the object and can be used to implement the Singleton pattern.