C#/.NET interview Question - Why Arrays are faster than ArrayList?

 Posted by ArticlesMaint on 4/23/2011 | Category: C# Interview questions | Views: 5074

Let’s demonstrate an example to prove that how arrays are faster than arraylist for that go to visual studio and create a simple window application with a button and two labels like below diagram.


Below is the code snippet.

using System.Collections;// import this namespace to access arraylist.
using System.Diagnostics;// import this namespace to access Stopwatch.
namespace ArrayandArrayList
public partial class Form1 : Form
int[] Array = new int[1000]; // here array is declared.
ArrayList objArraylist = new ArrayList();// here array list is declared.
public Form1()

private void button1_Click(object sender, EventArgs e)
Stopwatch objWatch = new Stopwatch();
Stopwatch objWatch1 = new Stopwatch();
for(int i=0;i<1000;i++)
Array[i] = DateTime.Now.Second;
foreach (int i in Array)

label1.Text = objWatch.ElapsedTicks.ToString();
for (int i = 0; i < 1000; i++)
foreach (object i in objArraylist)
label2.Text = objWatch1.ElapsedTicks.ToString();
In the above code, I have used Stopwatch to record the time taken by the array and  arraylist to performance actions.

The Output look like below diagram.


Conclusion: -As in ArrayList lots of Boxing and UnBoxing are done therefore its performance is slower than Array because in Array there is no type casting.


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Comments or Responses

Posted by: Akiii on: 4/25/2011
Good practical example...

Thanks and Regards

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