[.NET Internals 07] Unmanaged resources: finalization, fReachable queue and dispose pattern

Today we’re going to see how unmanaged resources are handled by .NET, what are finalization and fReachable queues and what’s the garbage collector’s role in it. We’ll also get to know what is a dispose pattern and see how to implement it.

Unmanaged resources and finalizers

First of all we should all get familiar with what unmanaged resources are. These ones can be files or folders on the disk, database connections, GUI elements or network resources. You can also think of them as some external elements we need to interact with in our applications through some protocol (e.g. database queries or file system manipulation methods). They’re called unmanaged not without a reason – any unmanaged resources accessed from .NET code will not be automatically cleaned by the garbage collector. That’s how they are not(un)managed. Maybe you’ve heard about

destructors in C++

[.NET Internals 01] Basics of memory structure

Have you ever wondered about what’s under the hood of the applications you develop? Ever been surprised that there’s no need to worry about memory allocation and deallocation using high-level programming languages such as Java or C# after leaving the university? Still remember (old) C++ times with delete statement?
Source: “Arnaud Porterie – The Truth About C++”
By this post, I’d like to introduce a new “.NET Internals” series on the blog. I will be publishing a new post on .NET internal concepts every Wednesday. No end date for the moment 🙂 Posts within the series will be mostly about memory management and performance aspects of .NET applications. All discussed concepts are applicable to most of the modern programming platforms, but the examples will be based on .NET Framework. If you’re interested in such topics, I encourage you to check this blog every Wednesday starting today 🙂 *there is 1 assumption and 1 fact here:
  • assumption: you used to program in C/C++ (before C++11) on the university,
  • fact: that’s not true you don’t need to worry about memory management using high-level programming languages; wait for the next posts to get to know why.


Each application targeting .NET is managed by CLR (Common Language Runtime), which is a part of .NET Framework, which must be installed on the computer on which the .NET application is launched – the exception are

.NET Core self-contained apps