Question

So, basically I am practicing some algorithms. And I am trying to figure out why the following code is giving me an error when I try to set the value of number[i]? I know it is probably simple but I don’t ‘why’ it does not work.

public int SumOfRandomNumbersWithStrings(string randomness)
{
    //Get the value of each index in the array
    string number = "";
    for (int i = 0; i < randomness.Length; i++)
    {
        number[i] = randomness[i];
    }
    //temporarily one until I finish the algorithm
    return 1;
}

Answer 1

why the following code is giving me an error when I try to set the value of number[i]

Because strings in C# are immutable.

Arrays of characters are mutable, though, so you can do this:

char number[] = new char[randomness.Length];
for (int i = 0; i < randomness.Length; i++)
{
     number[i] = randomness[i];
}
string numStr = new string(number);
//temporarily one until I finish the algorithm
return 1;

The most common way of building strings in C# is by using the StringBuilder class. It lets you change the content of the string by appending, removing, or replacing characters inside the string.