Array foreach int Array Lambda Odd, Even Predicate true, false

`Array.TrueForAll`

This is a static Array method. It gives you a declarative way to test every element in your array for some condition using a Predicate.

TrueForAll scans the array and returns true or false. The Predicate is invoked for each element in the array. We determine whether it returns true for all elements.

First example

We demonstrate the Array.TrueForAll method. Our program uses an int array of 4 odd numbers. The Array.TrueForAll method is invoked and the predicate is specified.

Argument 1 This is the array that we are testing. In this program, this is the array of 4 integers called "values."

Argument 2 This is a predicate lambda. The predicate method returns true whenever a number is not evenly divisible by two.

using System;

int[] values = { 1, 3, 5, 7 };
// See if modulo 2 is 1 for all elements.
bool result = Array.TrueForAll(values, y => y % 2 == 1);
Console.WriteLine("TRUEFORALL: {0}", result);
TRUEFORALL: True

Example, false

Here the numbers in the array are not all odd. Therefore the same Array.TrueForAll parameters will have the method return false.

Info We see that Array.TrueForAll correctly applies the predicate to every element in the array.

using System;

int[] values = { 2, 5, 8 };
// Test for all odd numbers again.
bool result = Array.TrueForAll(values, y => y % 2 == 1);
Console.WriteLine("RESULT: {0}", result);
RESULT: False

Discussion

We could write a method that does the same thing as Array.TrueForAll. This method would test each element in a foreach-loop, and return early if an element doesn't match.

Info Typically, this sort of approach is much faster than using a call such as Array.TrueForAll.

However Array.TrueForAll is less familiar to programmers used to other languages. Its use might make a development team less efficient.

Array.TrueForAll can simplify some programs. By applying the predicate argument to each element, we can test every element of the array for some condition.