C# | Array.TrueForAll() Method

This method is used to determine whether every element in the array matches the conditions defined by the specified predicate.
Syntax:

public static bool TrueForAll (T[] array, Predicate<T> match);

Here, T is the type of element of the array.
Parameters:

array: It is the one-dimensional, zero-based Array to check against the conditions. 
match: It is the predicate that defines the conditions to check against the elements. 

Return Value: This method returns true if every element in the array matches the conditions defined by the specified predicate otherwise it returns false. If there are no elements in the array, the return value is true.
Exception: This method throws ArgumentNullException if the array is null or the match is null.
Below programs illustrate the use of Array.TrueForAll(T[], Predicate) Method:
Example 1:

CSHARP

// C# program to demonstrate
// TrueForAll() method
using System;
using System.Collections.Generic;

public class GFG {

// Main Method
public static void Main()
{

    try {

        // Creating and initializing new the String
        String[] myArr = {"Sun", "Son", "Sue", "Shu"};

        // Display the values of the myArr.
        Console.WriteLine("Initial Array:");

        // calling the PrintIndexAndValues()
        // method to print
        PrintIndexAndValues(myArr);

        // getting the bool value
        // with required condition
        // using method TrueForAll()
        bool value = Array.TrueForAll(myArr, element => element.StartsWith("S",
                                                    StringComparison.Ordinal));

        // Checking the condition
        if (value)
            Console.Write("Every Element is satisfying condition");
        else
            Console.Write("Every Element is not satisfying condition");
    }
    catch (ArgumentException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}

// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(String[] myArr)
{
    for (int i = 0; i < myArr.Length; i++) {

        Console.WriteLine("{0}", myArr[i]);
    }
    Console.WriteLine();
}
}

Output:

Initial Array:
Sun
Son
Sue
Shu

Every Element is satisfying condition

Example 2: For ArgumentNullException

CSHARP

// C# program to demonstrate
// TrueForAll() method
// For ArgumentNullException
using System;
using System.Collections.Generic;

public class GFG {

// Main Method
public static void Main()
{

    try {

        // Creating and initializing new
        // the String with a null value
        String[] myArr = null;

        // getting the bool value
        // with required condition
        // using method TrueForAll()
        Console.WriteLine("Trying to get the boolean "
                        +"value while myArr is null");
        Console.WriteLine();
        bool value = Array.TrueForAll(myArr, element => element.StartsWith("S",
                                                    StringComparison.Ordinal));

        // Checking the condition
        if (value)
            Console.Write("Every Element is satisfying condition");
        else
            Console.Write("Every Element is not satisfying condition");
    }
    catch (ArgumentException e) {

        Console.Write("Exception Thrown: ");
        Console.Write("{0}", e.GetType(), e.Message);
    }
}

// Defining the method
// PrintIndexAndValues
public static void PrintIndexAndValues(String[] myArr)
{
    for (int i = 0; i < myArr.Length; i++) {

        Console.WriteLine("{0}", myArr[i]);
    }
    Console.WriteLine();
}
}

Output:

Trying to get the boolean value while myArr is null

Exception Thrown: System.ArgumentNullException

Reference:

• https://docs.microsoft.com/en-us/dotnet/api/system.array.trueforall?view=netframework-4.7.2