Help me understand this please!!!!

Question

Hello, im a programmer stundent im doing a project about Cua(Queue in catalan), its a dynamic queue where the data are stored in Nodes, and i want to understand why, in the next code i can use the .Count to get the total of the nodes linked in the queue:

My teacher said its for System.Linq; and chat gpt said its for System.Collections.Generic;

but in my code i DELETED this two sentences and the program and the .Count still working correctly, for last i created a new project from 0, without linq and system collections to see if it was a cache problem, and still working well.

Help me understand why this still working.

I left my Code here: (its all the code, i checket theres no Count method anywere!):

https://github.com/GuiltyIsaac/HELP-

Answer 1

LINQ provides extension methods on any type that implements IEnumerable<T> which is defined in the System.Collections.Generic namespace and is the general interface you use for anything that stores sets of items including List<T> and Queue<T>.

LINQ has an extension method Count that returns the # of items in the collection by enumerating them and adding up the total. As such any IEnumerable<T> implementation has this method available to it. It looks like an instance method but is in fact a static method on the Enumerable class. Read about extension methods to understand how this works.

Enumerable is defined in the System.Linq namespace along with a lot of the other LINQ-based types. Therefore by including that namespace you have access to the extension methods.

using System;
using System.Collections.Generic;
using System.Linq;

public class SomeClass
{
   public void DoWork ()
   {
      Queue<int> numbers = new Queue<int>();
      for (int index = 1; index <= 10; ++index)
          numbers.Enqueue(index);

      int count = numbers.Count();  //Extension method Enumerable.Count()       

      //Note: List<T> has a Count property which does the same thing, but only for List<T>
   }
}

If you are compiling using .NET 6+ AND your project has implicit usings enabled then the compiler automatically includes some of the more commonly needed namespaces automatically at the top of your source files including: System, System.Collections.Generic and System.Linq. As such this eliminates the need for you to have these commonly needed namespaces explicitly listed in every source file you have. The earlier code can be rewritten without them and the compiler will generate the same exact code.

public class SomeClass
{
   public void DoWork ()
   {
      Queue<int> numbers = new Queue<int>();
      for (int index = 1; index <= 10; ++index)
          numbers.Enqueue(index);

      int count = numbers.Count();  //Extension method Enumerable.Count()       

      //Note: List<T> has a Count property which does the same thing, but only for List<T>
   }
}

By default when you create a NET 6+ project then implicit usings are enabled in the project. You can disable them in the project file but there probably isn't a good reason to do so.