ArrayList
Here we get the number of
elements in an ArrayList, which is a non-generic collection that stores its
length in a property called Count. This is identical to the List collection,
which we will see next. This property access is fast.
Program that
uses ArrayList: C#
using System;
using
System.Collections;
class
Program
{
static void Main()
{
ArrayList ar = new ArrayList();
ar.Add("One");
ar.Add("Two");
// Count the elements in the
ArrayList.
int c = ar.Count;
Console.WriteLine(c);
}
}
Output
2
List
Here we use List, a generic
collection. You must specify its type in the sharp angle brackets <T>.
These collections have superior performance and usually preferable. List has a
property called Count that is fast to access.
Program that
uses List: C#
using
System;
using
System.Collections.Generic;
using
System.Linq;
class
Program
{
static void Main()
{
List<int> list = new
List<int>();
list.Add(1);
list.Add(2);
// Count with the Count property.
int c = list.Count;
Console.WriteLine(c);
}
}
Output
2
Arrays
Arrays are counted differently and you need to use Length. In programs,
an array's size is set differently than List or ArrayList, and it does not grow
dynamically. The Length value will include all elements.
Count extension
You can use the Count() extension method when you have an IEnumerable collection or are using LINQ statements. Enumerations in C# are collections that haven't been determined exactly yet, and they can use yield and foreach keywords.Program that uses LINQ: C#
using System;
using System.Linq;
class Program
{
static void Main()
{
string[] arr = new string[]
{
"One",
"Two",
"Three"
};
// An enumerable collection, not in memory yet.
var e = from s in arr
select s;
int c = e.Count();
Console.WriteLine(c);
}
}
Output
3
