When should I create a destructor

Question

For example   public class Person       public Person                     Person                   When should I manually create a destructor  When have you needed to create a destructor

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It s called a destructor finalizer  and is usually created when implementing the Disposed pattern   It s a fallback solution when the user of your class forgets to call Dispose  to make sure that  eventually  your resources gets released  but you do not have any guarantee as to when the destructor is called   In this Stack Overflow question  the accepted answer correctly shows how to implement the dispose pattern  This is only needed if your class contain any unhandeled resources that the garbage collector does not manage to clean up itself   A good practice is to not implement a finalizer without also giving the user of the class the possibility to manually Disposing the object to free the resources right away

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UPDATE  This question was the subject of my blog in May of 2015  Thanks for the great question   See the blog for a long list of falsehoods that people commonly believe about finalization      When should I manually create a destructor     Almost never    Typically one only creates a destructor when your class is holding on to some expensive unmanaged resource that must be cleaned up when the object goes away  It is better to use the disposable pattern to ensure that the resource is cleaned up  A destructor is then essentially an assurance that if the consumer of your object forgets to dispose it  the resource still gets cleaned up eventually   Maybe    If you make a destructor be extremely careful and understand how the garbage collector works  Destructors are really weird    They don t run on your thread  they run on their own thread  Don t cause deadlocks  An unhandled exception thrown from a destructor is bad news  It s on its own thread  who is going to catch it  A destructor may be called on an object after the constructor starts but before the constructor finishes  A properly written destructor will not rely on invariants established in the constructor  A destructor can  resurrect  an object  making a dead object alive again  That s really weird  Don t do it  A destructor might never run  you can t rely on the object ever being scheduled for finalization  It probably will be  but that s not a guarantee    Almost nothing that is normally true is true in a destructor  Be really  really careful  Writing a correct destructor is very difficult      When have you needed to create a destructor    When testing the part of the compiler that handles destructors  I ve never needed to do so in production code  I seldom write objects that manipulate unmanaged resources

User · Answer

When you have unmanaged resources and you need to make sure they will be cleaned up when your object goes away   Good example would be COM objects or File Handlers

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You don t need one unless your class maintains unmanaged resources like Windows file handles

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I have used a destructor  for debug purposes only  to see if an object was being purged from memory in the scope of a WPF application   I was unsure if garbage collection was truly purging the object from memory  and this was a good way to verify

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It s called a  finalizer   and you should usually only create one for a class whose state  i e   fields  include unmanaged resources  i e   pointers to handles retrieved via p invoke calls    However  in  NET 2 0 and later  there s actually a better way to deal with clean-up of unmanaged resources  SafeHandle   Given this  you should pretty much never need to write a finalizer again

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Destructors provide an implicit way of freeing unmanaged resources encapsulated in your class  they get called when the GC gets around to it and they implicitly call the Finalize method of the base class  If you re using a lot of unmanaged resources it is better to provide an explicit way of freeing those resources via the IDisposable interface  See the C  programming guide  http   msdn microsoft com en-us library 66x5fx1b aspx

[c#] When should I create a destructor?

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