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

Last Updated : 26 Nov, 2022

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:

CSharp

// 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)); 
    } 
} 

Output:

Elements Present in List:

0
2
4
6
8
10
 
Result: True

Example 2:

CSharp

// 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("Python 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");
    }
}

Output:

Elements Present in List:

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

Reference:

https://docs.microsoft.com/en-us/dotnet/api/system.collections.generic.list-1.trueforall?view=netframework-4.7.2

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