Microsoft .Net - FAQ

13. How does Microsoft .Net manage Memory? What is Garbage Collection?

The Microsoft .NET Framework is a managed type-safe environment for developing .Net applications and employs an automatic memory management scheme called garbage collection. Memory from objects that are no longer used is traced and reclaimed without any action required by the application.

The CLR frees the developer from the burden of managing memory (allocating and freeing up when done); instead it does the memory management itself. Memory is allocated to instantiations of .NET types (objects) from the managed heap, a pool of memory managed by the CLR. As long as there exists a reference to an object, the object is considered to be in use by the CLR. When there is no reference to an object, or it goes out of scope, and thus cannot be reached or used, it becomes garbage. However, it still holds on to the memory allocated to it. The Microsoft .NET Framework includes a Garbage Collector which runs periodically, on a separate thread. The Garbage Collector (GC) is a low-priority thread under normal circumstances. It operates when processor time is not consumed by more important tasks. When memory becomes limited, however, the Garbage Collector thread moves up in priority. Memory is reclaimed at a more rapid pace until it is no longer limited, at which point the priority of garbage collection is again lowered.

The Garbage Collector (GC) is non-deterministic. This approach to memory reclamation seeks to maximize application performance and supplies a less bug-prone application environment. Because of the mechanism by which garbage collection operates, you cannot be certain when an object will be reclaimed. Thus, you have no control over when a class's destructor (Visual C#) or finalizer (Visual Basic .NET) is executed. These methods should not contain code that you rely on being run at a given time. Instead, classes should implement a Dispose() method to explicitly free those resources when the class is no longer needed.

14. What versions of Microsoft .Net are available?

Microsoft started development on the .NET Framework in the late 1990s, originally under the name of Next Generation Windows Services (NGWS). By late 2000, the first beta versions of Microsoft .NET 1.0 were being released.

Version	Version Number	Release Date
1.0	1.0.3705.0	2002-01-05
1.1	1.1.4322.573	2003-04-01
2.0	2.0.50727.42	2005-11-07
3.0	3.0.4506.30	2006-11-06
3.5	3.5.21022.8	2007-11-19

The Microsoft .NET Framework is included with Windows Server 2003, Windows Server 2008 and Windows Vista, and can be installed on some older versions of Windows like Windows 2000 and Windows XP.