如何在C＃中的构造函数中创建对象的静态列表？

Question

I want to maintain a list of all instances of my class that are created. I thought I could do that by adding 'this' to a static list from within the constructor. Of course C# doesn't let me reference 'this' in the constructor because it's not fully constructed yet. That makes sense but I'm trying to figure out the best way to accomplish this.

class Thing
{ static List<Thing> AllTheThings;

  public Thing()
  { 
    AllTheThings.Add(this);  // can't reference 'this' here
  }

}

I can think of two ways to this:

1. Make the constructors private and create a static method ('MakeNewThing') that invokes the constructor and adds the new instance to the list. I worry about potential problems with not having a public constructor but I'm not sure what they are.
2. Create a shell class ('ThingShell') that contains Thing's. The constructor for ThingShell creates a Thing and adds it to the list. This is messy and requires ThingShell to proxy all of Thing's members.

I seem to remember doing something like this in C++ about 20 years ago but don't recall the details and can't find the code.

Anyone have a better ideas?

Answer 1

As @Jon Skeet said, that reference to "this" should have been fine. But just in case, here is an alternate method.

public class Thing
{
    public readonly static List<Thing> AllTheThings = new List<Thing>();

    //making the constructor private so that no other code can call it.
    private Thing() {  }

    //providing a static instance method for creating the object
    public static Thing Instance()
    {
        var t = new Thing();
        Thing.AllTheThings.Add(t);
         return t;
    }
}

Now, the thing (excuse the pun) to watch out for in this implementation is that, by having this static list of all "Things" instantiated by the app, you will run the risk of a memory sinkhole if you do not have a way to get rid of old "Things" when they are no longer needed within scope.