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New Message on BDOTNET
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From: Anand_2004
Message 1 in Discussion
Hi Folks,
Today I am covering Generics .This is one of the great feature of C# 2.0
infect I like it very much. Generics has lots of cool stuffs .I am going to
write a series of articles in order to cover it in-detail. This is first part
of my article on Generics.Generics is a mechanism that encapsulate operations
that are not specific to any particular data type, that means it allows
classes or structs or interfaces or methods to be parameterized by the types
of data they store and manipulate. Generics provides the benefits like
reusability, type safety and efficiency in a way that their non-generic
counterparts cannot. Generics are most commonly used with collections and the
methods that operate on them. The .NET framework 2.0 provides a new namespace
System.Collections. Generics which contains several new generics based
collection classes apart from this you can also create custom generic types and
methods to provide your own generalized solutions that are type-safe and
efficient.
If we look at the collection classes of .NET Framework 1.X there are certain
limitations like it needs to perform boxing/unboxing or
up-casting/down-casting while storing and retrieving of values for example if
we store value type in ArrayList it performs boxing/unboxing or if store
string in ArrayList it performs up-casting and down-casting because it takes
System.Object as parameter , the other limitation is lack of compile-time type
checking; since an ArrayList casts everything to Object to over come the above
problems in .NET framework 1.X we can write our own type specific collection
class ( custom collection class) but again such class are not generic (
reusable) for more than one data type and you have to rewrite different custom
class for each data types.
The ultimate solutions to this problems is ArrayList needs a type parameter.
That is precisely what generics provide. In the generic List<T> collection, in
the System.Collections.Generic namespace, the same operation of adding items to
the collection looks like this
List<int> mylist = new List<int>();<O:P> </O:P>
//No boxing, no casting:<O:P> </O:P>
mylist.Add(99); <O:P></O:P>
//Compile-time error:<O:P> </O:P>mylist.Add("Wrong type passed");
Similarly you can define your custom generic class for example
public class MyList <T>
{
T[] items;
int counter;
public void Add ( T item)
{
// code here
}
public void Remove (T item)
{
// code here
}
}
in the above example generics provide a facility for creating types that have
type parameters ( MyList class with type parameter T). While instantiating
MyList<T> specify the type for which they are created and store data of that
type without conversion to and from System.Object. Actually the type parameter
<T> acts as a placeholder until an actual type is specified at use as below
MyList<int> objList = new MyList<int>();
objList.Add(3); // this eliminate boxing/unboxing or casting operation and
provide strong type
its a compile time error is we add text to this list fro example
objList.Add("This is a test message");//compile-time error
The above example demonstrate only one type , Generic type declarations may
have any number of type parameters lets say for hashtable we need key and value
for this you need to specify the number of parameters while define the class as
below
public class MyHash<T Key,T Value>
{
//reset of the code here
}
Cheers
Anand
http://spaces.msn.com/members/anandkumar
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