How to get all elements of a List

Return value: This method returns a List<T> containing all the elements that match the conditions defined by the specified predicate otherwise it returns an empty List<T>.

Exception: This method will give ArgumentNullException if the match is null.

Below programs illustrate the use of List<T>.FindAll(Predicate<T>) Method:

 

Example 1:

// C# Program to get all the element that 
// match the specified conditions defined 
// by the predicate 
using System; 
using System.Collections; 
using System.Collections.Generic; 
  
class Geeks { 
  
    // function which checks whether an 
    // element is even or not. Or you can 
    // say it is the specified condition 
    private static bool isEven(int i) 
    { 
        return ((i % 2) == 0); 
    } 
  
    // Main Method 
    public static void Main(String[] args) 
    { 
  
        // Creating an List<T> of Integers 
        List<int> firstlist = new List<int>(); 
  
        // Adding elements to List 
        firstlist.Add(2); 
        firstlist.Add(4); 
        firstlist.Add(7); 
        firstlist.Add(2); 
        firstlist.Add(3); 
        firstlist.Add(2); 
        firstlist.Add(4); 
  
        Console.WriteLine("Elements Present in List:\n"); 
  
        // Displaying the elements of List 
        foreach(int k in firstlist) 
        { 
            Console.WriteLine(k); 
        } 
  
        Console.WriteLine(" "); 
  
        Console.Write("Elements that Match: \n"); 
  
        // Will give the List of Elements that 
        // match the conditions defined by predicate 
        List<int> Result = new List<int>(firstlist.FindAll(isEven)); 
  
        foreach(int i in Result) 
        { 
            Console.WriteLine(i); 
        } 
    } 
} 

 

Example 2:

// C# Program to get all the element that 
// match the specified conditions defined 
// by the predicate 
using System; 
using System.Collections; 
using System.Collections.Generic; 
  
class Geeks { 
  
    // function which checks whether an 
    // element is even or not. Or you can 
    // say it is the specified condition 
    private static bool isEven(int i) 
    { 
        return ((i % 2) == 0); 
    } 
  
    // Main Method 
    public static void Main(String[] args) 
    { 
  
        // Creating an List<T> of Integers 
        List<int> firstlist = new List<int>(); 
  
        // Adding elements to List 
        firstlist.Add(17); 
        firstlist.Add(77); 
        firstlist.Add(15); 
        firstlist.Add(9); 
        firstlist.Add(3); 
        firstlist.Add(7); 
        firstlist.Add(57); 
  
        Console.WriteLine("Elements Present in List:\n"); 
  
        // Displaying the elements of List 
        foreach(int k in firstlist) 
        { 
            Console.WriteLine(k); 
        } 
  
        Console.WriteLine(" "); 
  
        Console.Write("Result is: "); 
  
        // Will give the List of Elements that 
        // match the conditions defined by predicate 
        // Here no even number found in the list 
        // so it wil return an empty list 
        List<int> Result = new List<int>(firstlist.FindAll(isEven)); 
  
        // checking for the resultant 
        // Elements in the List 
        if ((Result.Count) == 0) { 
            Console.WriteLine("No Match Found"); 
        } 
    } 
}