Programming C# 8.0

Chapter 7. Object Lifetime

One benefit of .NET’s managed execution model is that the runtime can automate most of your application’s memory management. I have shown numerous examples that create objects with the new keyword, and none has explicitly freed the memory consumed by these objects.

In most cases, you do not need to take any action to reclaim memory. The runtime provides a garbage collector (GC),¹ a mechanism that automatically discovers when objects are no longer in use, and recovers the memory they had been occupying so that it can be used for new objects. However, there are certain usage patterns that can cause performance issues or even defeat the GC entirely, so it’s useful to understand how it works. This is particularly important with long-running processes that could run for days (short-lived processes may be able to tolerate a few memory leaks).

The GC is designed to manage memory efficiently, but memory is not the only limited resource you may need to deal with. Some things have a small memory footprint in the CLR but represent something relatively expensive, such as a database connection or a handle from an OS API. The GC doesn’t always deal with these effectively, so I’ll explain IDisposable, the interface designed for dealing with things that need to be freed more urgently than memory.

Value types often have completely different rules governing their lifetime—some local variable values live only for as long as their containing method runs, for example. Nonetheless, ...