OfType « Linq Operators « LINQ

OfType accepts a nongeneric IEnumerable collection and emit a generic IEnumerable<T> sequence that you can subsequently query:

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

class Program
{
    static void Main()
    {
        ArrayList classicList = new ArrayList();  // in System.Collections 
        classicList.AddRange(new int[] { 3, 4, 5 });
        IEnumerable<int> sequence1 = classicList.OfType<int>();

        foreach (int i in sequence1)
        {
            Console.WriteLine(i);
        }
    }
}


3
4
5

When encountering an incompatible type OfType ignores the incompatible element.

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

class Program
{
    static void Main()
    {
        ArrayList classicList = new ArrayList();  // in System.Collections 
        classicList.AddRange(new int[] { 3, 4, 5 });

        IEnumerable<int> sequence1 = classicList.Cast<int>();
        foreach (int i in sequence1)
        {
            Console.WriteLine(i);
        }
        DateTime offender = DateTime.Now;
        classicList.Add(offender);
        sequence1 = classicList.OfType<int>(); // OK - ignores offending DateTime 

        foreach (int i in sequence1)
        {
            Console.WriteLine(i);
        }
    }
}