.NET Garbage collector does almost all clean up activity for your objects. But
unmanaged resources (For example, Windows API created objects, File, Database connection objects,
COM objects, etc) is outside the scope of .NET framework we have to explicitly clean our
resources. For these types of objects, .NET framework provides Object.Finalize method, which can be
overridden and clean up code for unmanaged resources can be put in this section.
For example, lets say there are three objects: Object1, Object2, and Object3.
Object2 has the finalize method overridden and remaining objects do not have the
finalize method overridden.
Now when garbage collector runs for the first time it searches for objects whose
memory has to free. He can see three objects but only cleans the memory for Object1 and
Object3. Object2 it pushes to the finalization queue.
Now garbage collector runs for the second time. The garbage collector gets to know there are no objects to
be released and then checks for the finalization queue and at this moment, it clears object2
from the memory.
So if you notice that object2 was released from memory in the second round and
not first. That is why the best practice is not to write clean up Non .NET resources in Finalize
method rather use the DISPOSE.
Dispose method belongs to ‘IDisposable’ interface. We had seen in the previous
section how bad it can be to override the finalize method for writing the cleaning of unmanaged
resources. So if any object wants to release its unmanaged code best is to implement IDisposable
and override the Dispose method of IDisposable interface. Now once your class has exposed
the Dispose method it is the responsibility of the client to call the Dispose method to do
Now here question arise why we use Dispose Method
To use or override dispose method, implement Idisposable interface in
your class that comes under System namespace. The following example is a class that
implements IDisposable interface for cleaning object of file.
publicclass disposeexample: IDisposable
// Flag: Has Dispose already been called?
bool disposed = false;
private FileStream filestream;
private StreamReader streamreader;
filestream = new FileStream(Path.Combine(Environment.CurrentDirectory, "TextFile1.txt"), FileMode.Open, FileAccess.Read);