C# | Check if every List element matches the predicate conditions

List<T>.TrueForAll(Predicate<T>) is used to check whether every element in the List<T> matches the conditions defined by the specified predicate or not.

Syntax:

public bool TrueForAll (Predicate<T> match);

Parameter:

match: It is the Predicate<T> delegate which defines the conditions to check against the elements.

Return Value: This method returns true if every element in the List<T> matches the conditions defined by the specified predicate otherwise it returns false. If the list has no elements, the return value is true.

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

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

Example 1:

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// C# Program to check if every element 
// in the List matches the conditions 
// defined by the specified 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 a List<T> of Integers 
        List<int> firstlist = new List<int>(); 
  
        // Adding elements to List 
        for (int i = 0; i <= 10; i+=2) { 
            firstlist.Add(i); 
        
  
        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: "); 
  
        // Checks if all the elements of firstlist
        // matches the condition defined by predicate 
        Console.WriteLine(firstlist.TrueForAll(isEven)); 
    

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Output:

Elements Present in List:

0
2
4
6
8
10
 
Result: True

Example 2:

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// C# Program to check if every element 
//in the List matches the conditions 
//defined by the specified predicate
using System;
using System.Collections; 
using System.Collections.Generic;
  
public class Example
{
    public static void Main()
    {
        List<string> lang = new List<string>();
  
        lang.Add("C# language");
        lang.Add("C++ language");
        lang.Add("Java language");
        lang.Add("Pyhton language");
        lang.Add("Ruby language");
          
        Console.WriteLine("Elements Present in List:\n"); 
  
        foreach(string language in lang)
        {
            Console.WriteLine(language);
        }
  
        Console.WriteLine(" "); 
  
        Console.Write("TrueForAll(EndsWithLanguage): ");
  
        // Checks if all the elements of lang
        // matches the condition defined by predicate 
        Console.WriteLine(lang.TrueForAll(EndsWithLanguage));
    }
  
    // Search predicate returns 
    // true if a string ends in "language".
    private static bool EndsWithLanguage(String s)
    {
        return s.ToLower().EndsWith("language");
    }
}

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Output:

Elements Present in List:

C# language
C++ language
Java language
Pyhton language
Ruby language
 
TrueForAll(EndsWithLanguage): True

Reference:



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