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);
            }
        }
    }
}

You should change string b = s + "sad"; to string s += "sad"; — Kirill Bestemyanov
– Kirill Bestemyanov, Commented May 12, 2013 at 21:25
possible typo Console.WriteLine(b); instead of Console.WriteLine(s); — Emre
– Emre, Commented May 12, 2013 at 21:28

Marc Gravell · Accepted Answer · 2013-05-12 21:25:13Z

15

        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.

answered May 12, 2013 at 21:25

Marc Gravell

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Comments

Peter Mortensen · Accepted Answer · 2017-10-08 07:37:28Z

13

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

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

edited Oct 8, 2017 at 7:37

Peter Mortensen

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answered May 12, 2013 at 21:26

Tim Schmelter

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Comments

christopher · Accepted Answer · 2013-05-12 21:23:11Z

4

string b = s + "sad";

Console.WriteLine(s);

//Console.WriteLine(stringArray);

At no point in your code do you alter values in the array. You create a new string from each value in the array, concatenated with the string "sad".

Solution

You can not alter a for-each variable. You'll get a message like:

Cannot assign to 's' because it is a 'foreach iteration variable'.

Instead, settle for a simple for loop.

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

answered May 12, 2013 at 21:23

christopher

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Comments

Guffa · Accepted Answer · 2013-05-12 21:24:50Z

0

Look at this part of the code:

string b = s + "sad";
Console.WriteLine(s);

You are concatenating the string in s with the string "sad", and storing in the variable b. Then you display the content of the variable s. If you would display the content of the variable b isntead, there would be a sad at the end of each string.

answered May 12, 2013 at 21:24

Guffa

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