Language Integrated Query (LINQ): Part 3

First of all let's understand what "Arrays" are, what ".NET Collections" are and what ".NET Generic Collections" are. You will see the following advantages and disadvantages in the examples given below.

Now, let's discuss each of the collection types given in the above table to feel the real pain of development.

Array

If you use array:

ArrayList (System.Collection)

If you use ArrayList:

List<T> (System.Collection.Generic)

Now, in short we can say, a list has both the features that we have in arrays and arraylists.

Why we need List (which is generic type) in LINQ?

LINQ queries are based on generic types, which were introduced in version 2.0 of the .NET Framework. LINQ queries return collections and we don't even know what type of data we will get from the database and that is the reason we use a generic type like List<T>, IEnumerable<T>, IQueryable<T> etc. For example:

In the above example, we have used the IEnumerable<T> interface and a LINQ query and then by using a foreach loop I'm able to get my data.

One more example:

IEnumerable<Customer> customerQuery =

from cust in customers

where cust.City == "Bokaro"

select cust;

foreach (Customer customer in customerQuery)

{

Console.WriteLine(customer.LastName + " = " + customer.Age);

}

In the above example you can see, using a LINQ query I'm not only limited to select the string value that is LastName, I'm also able to select an integer value that is Age.

So, this could be the great example of generic classes.

Here is some counterpart of Generic Collections over non-generic collections: