int[] intArray = {1, 2, 3, 4, 5}; Array.Resize(ref intArray, intArray.Length + 1); intArray[intArray.Length - 1] = 6;In this example, we first create an array of integers with five elements. We then use the 'Resize' method to increase the size of the array by one. Finally, we add the new element (6) to the end of the array. Package/Library: The 'Add' method is a built-in method of the 'Array' class in C#, which is included in the System namespace. No additional package or library is required to use this method.