Question

How can I find out how many objects are created of a class in C#?

Answer 1

You’d have to put a static counter in that was incremented on construction:

public class Foo
{
    private static long instanceCount;

    public Foo()
    {
        // Increment in atomic and thread-safe manner
        Interlocked.Increment(ref instanceCount);
    }
}

A couple of notes:

• This doesn’t count the number of currently in memory instances – that would involve having a finalizer to decrement the counter; I wouldn’t recommend that
• This won’t include instances created via some mechanisms like serialization which may bypass a constructor
• Obviously this only works if you can modify the class; you can’t find out the number of instances of System.String created, for example – at least not without hooking into the debugging/profiling API

Why do you want this information, out of interest?