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New Message on BDOTNET
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From: SitaramanM
Message 2 in Discussion
Hi Anand Guess u are in a questioning spree :) Here you go What is the
Difference bet obj=null and obj.dispose() When you set the obj=-null what you
are doing essentially is to make the obj go out of scope and making it eligible for a
garbage collection later. When you set it to null, the reference is removed from the
application roots and therefore the Garbage Collector will consider this object for
collection.
Dispose however is a different story altogether. Dispose rather than a deallocator,
is basically a best practice. You do understand that .Net works in a GC mode Right!!!
Now it is possible that there could be unmanaged resources that your application
might be using and these need to be closed disposed off explicitly, example could
open file handles. Now where do you write code for closing these resources. in C++
yiou would have written it in destrcutors. As you know destructors are not there in
.Net. So you could write it in Finalize(However do note that Finalize is NOT the .Net
equivalent of destructors). The problem with finalize is that you will never know
when it will be called. So instead of depending on the runtime to close such
unmanaged resources which could happen anytime at the prerogative of GC, you would
rather write the cleanup code in dispose and ask he consumers of the class to call it
explicitly. What you also typically do is that you write the cleanup code in a
separate function , lets say cleanup() and then call this method from the both dispose
and finalize. This way, if the consumer of the class is decent enough to call the
dispose, then the cleanup will happen immdtly, if the consumer does not call dispose
then atleast finlize will do the cleanup( though it is not typically recommended to
perform time/resouirce intensive operations in finalize). One step furthur, you can
maintain flags in finalize and call he cleanup() function only if the dispose has not
already called it). Two steps furthus, taking a leaf from Roshan's proprietary(had to
lookup word for the spelling :) ) secrets(exposed, thanx to pandu), what you can also
do is to log the cleanup operations in finalize to check which developers had not
called dispose(thts a good one rosh!!!)
Apart from Overloading and overridding how can we acheive Polymorhism using
interface and abstract class. Apart from abstract/interfaces, One more exhibition
of polymorphism is the Generics concept in C# 2.0 specification. It is called
Parametricized polymorphism. Lookup the articles on Generics on the net. Btw one
point to note, Overriding happens only in the case of abstract class. In the case of
Interfaces it is not overriding rather it is implementation of the function. Though
there could be a lot of confusion over the diff btwn Interface v/s abstract class,
the standard is that an interface is a basically a contract and the implementation is
done in the classes that implement the interface. So i dont think it is right to call
a method implementation of a interface as overriding!!!! How data will be
passed to the remote Object. Two options By Value or By Ref. if you want By
Value, you go for serialization. Serialization could be Default Serialization that is
by decorating with the SerializableAttribute or it could b Custom Serialization that
is by implementing the ISerializable Interface. If you want ByRef then go for
inheriting the MarshalByRefObject. Such objects could be either Server
Activated(SAO) ot Client Activated(CAO). As far as the object formatting goes, in the
case of both ByVal(serialized) and ByRef(MarshalByRefObject), you can use either the
BinaryFormatter or the SoapFormatter. How to do optimistic and pesimistic
conditions in ADO.NET Check out the MSDN. has loads of material hth
regards, sr
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