Using a 'foreach' loop with stringArray in C#

Question

I am writing a program which should display the items from an array in a foreach loop.

I wanted to change the elements of the array by adding a string "sad" to each element, but when run the program the array stays the same.

namespace ConsoleApplication3
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] stringArray = {"hey", "Tom"};

            for (int i = 0; i < stringArray.Length; i++ )
            {
                stringArray[i] += "  dad";
                Console.WriteLine(stringArray[i]);
            }

            Array.Resize(ref stringArray, stringArray.Length + 1);

            // Add bob to the last element of the array
            stringArray[stringArray.Length - 1] =" bob";

            foreach (string s in stringArray)
            {
                string b = s + "sad";
                Console.WriteLine(s);
                //Console.WriteLine(stringArray);
            }
        }
    }
}

Answer 1

        foreach (string s in stringArray)
        {   
            string b = s + "sad";
            // ...
        }

Here you are creating a new string, completely unrelated to the string in the string-array. You haven't changed the old string (you can't; strings are immutable). You then simply drop this new longer string on the floor - you aren't updating the array etc.

Try instead something like:

for(int i = 0 ; i < stringArray.Length ; i++)
{
    stringArray[i] = stringArray[i] + "sad";
}

This replaces every item in the array with a new string. Note that you can't update a list/collection/array etc while iterating with foreach - that can break the iterator. Hence the for loop instead.

Answer 2

Apart from what Chris said, you could simply use LINQ to achieve what you want:

string[] newStringArray = stringArray
    .Select(s => s + "sad")
    .ToArray();