What is Garbage Collection in .NET?

Garbage Collection (GC) in .NET is the automatic memory management mechanism responsible for identifying objects that are no longer reachable by an application and reclaiming the memory they occupy. Developers generally don't need to explicitly allocate or release managed memory, which reduces risks such as memory leaks and invalid memory access.

.NET uses a generational garbage collector, primarily organizing managed objects into Generation 0, Generation 1, and Generation 2. Short-lived objects are collected more frequently, while long-lived objects are promoted to higher generations. Large allocations may be handled in the Large Object Heap (LOH).

A typical lifecycle is:

Object Allocation → Gen 0 → Survives GC → Gen 1 → Survives GC → Gen 2

From an expert perspective, understanding GC is important for application performance. Excessive allocations, unnecessary object retention, large object allocations, and inappropriate caching can increase GC pressure and cause latency.

Developers should also distinguish managed memory from unmanaged resources. GC manages managed objects, but resources such as file handles, database connections, and native resources should generally be released deterministically using patterns such as IDisposable and using.