Generate random different string

Question

I want to generate a different random string every time I use the function.

public static Dictionary<string, long> Giftcodes = new Dictionary<string, long>();

private static Random random = new Random();

        public static string GenerateCode()
        {
            string code = "";

            string chars = "abcefhijkmnorsuvwxyzABCDEFHIKMNORSUVWXYZ1234567890";

            if (Giftcodes.Keys == null)
            {
                code = new string(Enumerable.Repeat(chars, 16)
                    .Select(s => s[random.Next(s.Length)]).ToArray());
            }else
            {
                while (!Giftcodes.Keys.Contains(code))
                {
                    code = new string(Enumerable.Repeat(chars, 16)
                        .Select(s => s[random.Next(s.Length)]).ToArray());
                }
            }

            return code;
        }

I did a little bit of researches but I found nothing.

What's the question you have? – maraaaaaaaa Jun 27 '23 at 19:54 — maraaaaaaaa, Jun 27 '23 at 19:54

Guru Stron · Answer 1 · 2023-06-27T20:05:57.410

1

while (!Giftcodes.Keys.Contains(code)) looks very suspicious, basically it does the opposite - it will generate a code until it is present in the dictionary, try changing it to:

do
{
    code = ....
} 
while (Giftcodes.ContainsKey(code));

// ...

Giftcodes.Add(code, 0); // do not forget to add the code
return code;

Also:

Consider using Random.Shared.
Consider using HashSet<string> instead of dictionary if you don't need values
Maybe you will need Thread-safe collections if this is used in multithreaded environment.

edited Jun 27 '23 at 20:05

answered Jun 27 '23 at 19:55

Guru Stron

102,774
10
95
132

It gives me "System.NullReferenceException: 'Object reference not set to an instance of an object.'" at the this line of code "while (Giftcodes.ContainsKey(code))". – Security Support Jun 27 '23 at 20:00
@SecuritySupport [What is a NullReferenceException, and how do I fix it?](https://stackoverflow.com/questions/4660142/what-is-a-nullreferenceexception-and-how-do-i-fix-it). – Guru Stron Jun 27 '23 at 20:03
this is error that appears when I try to run the code. – Security Support Jun 27 '23 at 20:05
@SecuritySupport also see the update. – Guru Stron Jun 27 '23 at 20:05

Generate random different string

1 Answers1