Exists Method Implementation for Multidimensional Array in C#

Question

To determine whether the specified array contains specific element or not, Array.Exists can be used if the given array is one dimensional. I am attempting to implement Exists method for multidimensional array cases.

The experimental implementation

static class MDArrayHelpers
{
 public static bool Exists<T>(Array array, Predicate<T> match)
 where T : unmanaged
 {
 if (ReferenceEquals(array, null))
 {
 throw new ArgumentNullException(nameof(array));
 }
 Type elementType = array.GetType().GetElementType();
 if (!elementType.Equals(typeof(T)))
 {
 throw new System.InvalidOperationException();
 }
 foreach (var element in array)
 {
 if (match((T)element))
 {
 return true;
 }
 }
 return false;
 }
}

Test cases

Predicate<int> isOne = delegate (int number) { return number == 1; };
Predicate<int> isFour = delegate (int number) { return number == 4; };
Console.WriteLine("One dimensional case");
int[] array1 = new int[] { 1, 2, 3 };
Console.WriteLine($"Is one existed in {nameof(array1)}: {Array.Exists(array1, isOne)}");
Console.WriteLine($"Is four existed in {nameof(array1)}: {Array.Exists(array1, isFour)}");
Console.WriteLine("");
Console.WriteLine("Two dimensional case");
int[,] array2 = { { 0, 1 }, { 2, 3 } };
Console.WriteLine($"Is one existed in {nameof(array2)}: {MDArrayHelpers.Exists(array2, isOne)}");
Console.WriteLine($"Is four existed in {nameof(array2)}: {MDArrayHelpers.Exists(array2, isFour)}");
Console.WriteLine("");
Console.WriteLine("Three dimensional case");
int[,,] array3 = { { { 0, 1 }, { 2, 3 } }, { { 0, 1 }, { 2, 3 } } };
Console.WriteLine($"Is one existed in {nameof(array3)}: {MDArrayHelpers.Exists(array3, isOne)}");
Console.WriteLine($"Is four existed in {nameof(array3)}: {MDArrayHelpers.Exists(array3, isFour)}");
Console.WriteLine("");
Console.WriteLine("Four dimensional case");
int[,,,] array4 = { { { { 0, 1 }, { 2, 3 } }, { { 0, 1 }, { 2, 3 } } }, { { { 0, 1 }, { 2, 3 } }, { { 0, 1 }, { 2, 3 } } } };
Console.WriteLine($"Is one existed in {nameof(array4)}: {MDArrayHelpers.Exists(array4, isOne)}");
Console.WriteLine($"Is four existed in {nameof(array4)}: {MDArrayHelpers.Exists(array4, isFour)}");

The output of the test code above:

One dimensional case
Is one existed in array1: True
Is four existed in array1: False
Two dimensional case
Is one existed in array2: True
Is four existed in array2: False
Three dimensional case
Is one existed in array3: True
Is four existed in array3: False
Four dimensional case
Is one existed in array4: True
Is four existed in array4: False

If there is any possible improvement, please let me know.

Answer 1

You can simply use the LINQ Enumerable.Any extension Method.

bool result = array4.Cast<int>().Any(x => x == 1);

This works for any collection implementing IEnumerable<T> and also for enumerations created algorithmically by C# Iterators.

According the the C# Programming Guide (Arrays):

Array types are reference types derived from the abstract base type Array. Since this type implements IEnumerable and IEnumerable<T>, you can use foreach iteration on all arrays in C#.

This statement is, however, misleading, since we need to cast the array here. Obviously, we only have the access to the non-generic interface IEnumerable.

LINQ Extension methods found in the Enumerable Class apply to IEnumerable<T> or IEnumerable.

• JimmyHu: Thank you for answering. I found that error CS1061: 'int[*,*,*,*]' does not contain a definition for 'Any' and no accessible extension method 'Any' accepting a first argument of type 'int[*,*,*,*]' could be found occurred in array4.Any(x => x == 1), but array4.Cast<int>().ToList().Any(x => x == 1) can be used as a solution.
• aloisdg: The ToList() should not be needed
• Olivier Jacot-Descombes: Please, see also my follow up question: Is the C# Programming Guide right on pretending that arrays implement IEnumerable<T>?.
• Olivier Jacot-Descombes: @JimmyHu to use the Any LINQ extension method, you must import the corresponding namespace with using System.Linq;