.NET Managed Heap and Garbage Collection: How Object Lifetime Is Managed

new does more than create an instance. It asks the CLR to allocate an object on the managed heap. Allocation is often fast, but collection, compaction, and promotion still have runtime costs.

Why Tracing GC

Reference counting struggles with cycles. The CLR uses tracing GC: it starts from roots, finds reachable objects, and collects the rest.

Generational GC works because most objects are short-lived. Gen 0 is collected frequently, while long-lived objects are promoted to older generations.

Practical Advice

• Avoid creating many temporary objects in hot loops.
• Do not let static collections hold objects forever by accident.
• Dispose unmanaged resources such as file handles and network connections promptly.
• GC manages memory; it does not automatically manage every resource lifetime.