How to manage IDisposable Objects that are cached?

Question

I have an object that is expensive to create, which uses some unmanaged resources that must be explicitly freed when done with and so implement IDisposable(). I would like a ca

Answer 1

You can solve this with a class factory and IDisposable. For example:

public class CachedObject : IDisposable {
  private int mRefCount;
  private CachedObject(int something) {
    mRefCount = 1;
  }
  public static CachedObject CreateObject(int something) {
    CachedObject obj = LookupInCache(something);
    if (obj != null) Interlocked.Increment(ref obj.mRefCount);
    else obj = new CachedObject(something);
    return obj;
  }
  private static CachedObject LookupInCache(int something) {
    CachedObject obj = null;
    // Implement cache lookup here, don't forget to lock
    //..
    return obj;
  }
  public void Dispose() {
    int cnt = Interlocked.Decrement(ref mRefCount);
    if (cnt == 0) {
      // Remove from cache
      // 
    }
  }
}