Exists Method Implementation for Multidimensional Array in C#
You can simply use the LINQ Enumerable.Any extension Method.
bool result = array4.Cast&lt;int&gt;().Any(x =&gt; x == 1);

This works for any collection implementing IEnumerable&lt;T&gt; 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&lt;T&gt;, 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&lt;T&gt; or IEnumerable.