Both Dispose and Finalizer are used to clear resources. Finalizer is usually used to clear unmanaged resources like file handler, database connection handler, network socket handler etc and usually called by GC (CLR garbage collector) and it usually has performance issue since GC is usually forced to run whereas Dispose is usually used to clear both unmanaged resources and managed resources. Dispose is called manually by the developer so it does not have any performance issue like the Finalizer. To implement Dispose, developer has to implement the IDisposable interface and implement Dispose method.
Here is the example to illustrate them in C# console. I used console app so it can be easily demonstrated.
Above, I have a class ResourceHolder that implemented IDisposable interface
- In the constructor, I initialized the streamReader (file handler), collection List object , and a pointer that is used to simulate a pointer to the handler of unmanaged resource.
- Two public methods that one is for adding a list of file name and Read line by the stream reader
- I also have to implement void Dispose(). I made it virtual so any derived class can implement their own Dispose method.
- I have a private Dispose(bool isDisposing). isDisposing is used as a flag to indicate whether we want to clear managed resource as well. it is useful when we have to call it from the Finalizer.
- We have a flag isDisposed to check if unmanaged resources have already been cleared.
- In Finalizer() method ~ClassName(): we call our private Dispose(false) with isDisposing flage = false so to indicate that we only want to clear unmanaged resource.
- In our main program, we instantiate first object of ResourceHolder rh with using {…} which the compiler knows that it will have to call Dispose method automatically at the end curly bracket.
- We also instantiate 2nd object of ResourceHolder rh2 but this time we will use finalizer so we will have to force GC to run by calling GC.Collect and wait for it to finish before ending our demo program with GC. WaitForPendingFinalizers();
Sample source code of this demo can be found at my GitHub: https://tinyurl.com/2e33d9rz
Sample output from this demo program:
