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Why do some people use the Finalize method over the Dispose method?
In what situations would you use the Finalize method over the Dispose method and vice versa?
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The main difference between dispose() and finalize() is that the method dispose() has to be explicitly invoked by the user whereas, the method finalize() is invoked by the garbage collector, just before the object is destroyed.
Destructor implicitly calls the Finalize method, they are technically the same. Dispose is available with objects that implement the IDisposable interface. The destructor implicitly calls Finalize on the base class of the object.
The Finalize method is used to perform cleanup operations on unmanaged resources held by the current object before the object is destroyed. The method is protected and therefore is accessible only through this class or through a derived class.
“This method is inherently unsafe. It may result in finalizers being called on live objects while other threads are concurrently manipulating those objects, resulting in erratic behavior or deadlock.” So, in one way we can not guarantee the execution and in another way we the system in danger.
Unlike Finalize, developers should call Dispose explicitly to free unmanaged resources. In fact, you should call the Dispose method explicitly on any object that implements it to free any unmanaged resources for which the object may be holding references.
Dispose/Finalized Pattern. Microsoft recommends that you implement both Dispose and Finalize when working with unmanaged resources. The Finalize implementation would run and the resources would still be released when the object is garbage collected even if a developer neglected to call the Dispose method explicitly.
Microsoft recommends that you implement both Dispose and Finalize when working with unmanaged resources. The Finalize implementation would run and the resources would still be released when the object is garbage collected even if a developer neglected to call the Dispose method explicitly.
There is no performance costs associated with Dispose method. There is performance costs associated with Finalize method since it doesn't clean the memory immediately and called by GC automatically. If you want to implement Finalize method, it is recommended to use Finalize and Dispose method together as shown below:
The finalizer method is called when your object is garbage collected and you have no guarantee when this will happen (you can force it, but it will hurt performance).
The Dispose method on the other hand is meant to be called by the code that created your class so that you can clean up and release any resources you have acquired (unmanaged data, database connections, file handles, etc) the moment the code is done with your object.
The standard practice is to implement IDisposable and Dispose so that you can use your object in a using statment. Such as using(var foo = new MyObject()) { }. And in your finalizer, you call Dispose, just in case the calling code forgot to dispose of you.
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Others have already covered the difference between Dispose and Finalize (btw the Finalize method is still called a destructor in the language specification), so I'll just add a little about the scenarios where the Finalize method comes in handy.
Some types encapsulate disposable resources in a manner where it is easy to use and dispose of them in a single action. The general usage is often like this: open, read or write, close (Dispose). It fits very well with the using construct.
Others are a bit more difficult. WaitEventHandles for instances are not used like this as they are used to signal from one thread to another. The question then becomes who should call Dispose on these? As a safeguard types like these implement a Finalize method, which makes sure resources are disposed when the instance is no longer referenced by the application.
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Finalize is the backstop method, called by the garbage collector when it reclaims an object. Dispose is the "deterministic cleanup" method, called by applications to release valuable native resources (window handles, database connections, etc.) when they are no longer needed, rather than leaving them held indefinitely until the GC gets round to the object.
As the user of an object, you always use Dispose. Finalize is for the GC.
As the implementer of a class, if you hold managed resources that ought to be disposed, you implement Dispose. If you hold native resources, you implement both Dispose and Finalize, and both call a common method that releases the native resources. These idioms are typically combined through a private Dispose(bool disposing) method, which Dispose calls with true, and Finalize calls with false. This method always frees native resources, then checks the disposing parameter, and if it is true it disposes managed resources and calls GC.SuppressFinalize.
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