Will ignoring IDisposable cause memory leaks?

Question

In the comments to an answer I wrote we had a discussion about memory leaks and IDisposable where we didn't come to any real conclusion.

A class that handles unmanaged resources likely implements IDisposable. If ignore that and neither call Dispose nor wraps the object in a using - will that lead to the unmanaged resource being leaked? Or will it be properly cleaned up when the GC collects the object?

We can assume that the class handling the unmanaged resource has a correct implementation of IDisposable, including finalizer etc.

Answer 1

It will not cause a memory leak. In fact, Dispose has absolutely nothing to do with memory management.

It will create a resource-leak. And while the GC will usually clean it up, this could be too infrequent and too late.

Omitting Dispose (using) can slow down or even crash your App. In the case of file resources or Db connections it can even cause problems in other applications.

Answer 2

I will not cause managed memory leaks. It can cause leaks in referenced unmanaged code. But it's worse than that: memory on modern systems is plentiful enough that you can often get by for a while with a bad leak. Witness Mozilla Firefox: it used to (does it still?) leak like a sieve, and millions were happy to use it.

The bigger problem is other resources that may have nothing to do with memory at all. Examples include database connections, system I/O handles, socket handles, file handles, and the like. These are all items where you can easily create denial of service situations on your own system if you aren't careful to use IDisposable properly.