Can I get the instances of alive objects of a certain type in C#?

问题

This is a C# 3.0 question. Can I use reflection or memory management classes provided by .net framework to count the total alive instances of a certain type in the memory?

I can do the same thing using a memory profiler but that requires extra time to dump the memory and involves a third party software. What I want is only to monitor a certain type and I want a light-weighted method which can go easily to unit tests. The purpose to count the alive instances is to ensure I don't have any expected living instances that cause "memory leak".

Thanks.

回答1:

To do it entirely within the application you could do an instance-counter, but it would need to be explicitly coded and managed inside each class--there's no silver bullet that I'm aware of to let you query the framework from within the executing code to see how many instances are alive.

What you're asking for is really the domain of a profiler. You can purchase one or build your own, but it requires your application to run as a child process of the profiler. Rolling your own isn't an easy undertaking, by the way.

If you want to consider the instance counter it would have to be something like:

public class MyClass : IDisposable
    public MyClass()
    {
        ++ClassInstances;
    }

    public void Dispose()
    {
        --ClassInstances;
    }

    private static new object _ClassInstancesLock;
    private static int _ClassInstances;
    private static int ClassInstances
    {
        get
        {
            lock (_ClassInstancesLock)
            {
                return _ClassInstances
            }
        }
    }

This is just a really rough sample, no tests for compilation; 0% guarantee for thread-safety (critical for this type of approach) and it leaves the door wide open for Dispose to be called, the instance counter to decrement, but for the object not to properly GC. To diagnose that bundle of joy you'll need, you guessed it, a professional profiler--or at least windbg.

Edit: I just noticed the very last line of your question and needed to say that my above approach, as shoddy and failure-prone as it is, is almost guaranteed to deceive and lie to you about the true number of instances if you're experiencing a leak. The best tool, IMO, for attacking these problems is ANTS Memory Profiler. Version 5 is a double-edge in that they broke Performance and Memory profiler into two seperate SKUs (used to be bundled together) but Memory Profiler 5.0 is absolutely lightning fast. Profiling these problems used to be slow as molases, but they've gotten around it somehome.

Unless this is for a personal project with 0 intent of redistribution you should invest the few hundred dollars needed for ANTS--but by all means use it's trial period first. It's a great tool for exactly this kind of analysis.

回答2:

The only way I see to do this is without any form of instrumentation to use the CLR Profiling API to track object lifetimes. I'm not aware of any APIs available to the managed code to do the same thing, and, so far as I know, CLR doesn't keep the list of live objects anywhere (so even with profiler API you have to create the data structures for that yourself).

VB.NET has a feature where it lets you track objects in debugger, but it actually emits additional code specifically for that (which basically registers all created objects in internal list of weak references). You could do that as well, using e.g. PostSharp to post-process your assemblies.

来源：https://stackoverflow.com/questions/1123272/can-i-get-the-instances-of-alive-objects-of-a-certain-type-in-c

标签

winforms

c#-3.0