How to convert int array to int?

Question

What I would like to learn how to do is to convert an int array to an int in C#.

However I want to append the int with the values from the array.

Example:

Answer 1

And just for fun...

arr.Select((item, index) => new { Item = item, Power = arr.Length - (index - 1) }).ToList().ForEach(item => total += (int)(Math.Pow(10, item.Power) * item.Item));