How to query an ArrayList with LINQ

In this example, I will show how to query an ArrayList using Linq. Since ArrayList are non-generic IEnumerable collections, the type of variable in the collection must be explicitly declared in the linq query.

I already have a web application setup, so, I will just add a class called Person. This is a very simple class containing only 2 properties – FirstName and LastName. The code for the class is below.

Person Class

1. namespace WebApplication1.CSClass
2. {
3.     public class Person
4.     {
5.         public string FirstName { get; set; }
6.         public string LastName { get; set; }
7.  
8.         public override string ToString()
9.         {
10.             return FirstName + " " + LastName;
11.         }
12.     }
13. }

I will then add a web form where I will add an ArrayList, add Person objects to the collection and then query the collection using Linq. The code for this is below.

Query ArrayList with LINQ

1. using System;
2. using System.Collections.Generic;
3. using System.Linq;
4. using System.Web;
5. using System.Web.UI;
6. using System.Web.UI.WebControls;
7. using System.Collections;
8. using WebApplication1.CSClass;
9.  
10. namespace WebApplication1
11. {
12.     public partial class LinqText : System.Web.UI.Page
13.     {
14.         protected void Page_Load(object sender, EventArgs e)
15.         {
16.             GetList();
17.         }
18.  
19.         private void GetList()
20.         {
21.             ArrayList list = new ArrayList();
22.             list.Add(new Person { FirstName = "Scooby", LastName="Doo" });
23.             list.Add(new Person { FirstName = "Bugs", LastName = "Bunny" });
24.             list.Add(new Person { FirstName = "Peter", LastName = "Pan" });
25.  
26.             var q = from Person p in list
27.                     orderby p .FirstName
28.                     orderby p.LastName
29.                     select p;
30.  
31.             string br = "<br/>";
32.             foreach (Person p in q)
33.             {
34.                 L1.Text += p.ToString() + br;
35.             }
36.  
37.         }
38.     }
39. }

Note that, in the linq query, the object type is specified. The query will not work unless it is specified.