How to loop constructor to produce different values? c#

Question

0.00/5 (No votes)

See more:

I'm new to coding, and just working on a little project to learn.

I'm trying to produce multiple different versions of sets of attributes that I'll be inserting into a SQLite database.

My current code prints the same numbers each time, ie:

C#

... etc.

I guess it has to do with the constructor loop? Anyway I can't figure out why it is happening or how to solve it, any help or explanation would be greatly appreciated.

Thanks!

What I have tried:

C#

            for (int i = 0; i < 10; i++)
            {
                GenData gd = new GenData();
                gd.GenStats();
            }

//Above in method in different class to below.

    class GenData
    {
        
        public void GenStats()
        {

            Random rand = new Random();

            int[] arr = new int[4];

            for (int x = 0; x < arr.Length; x++)
            {

//Weighted probability of values

                if (rand.NextDouble() < 0.90)
                {
                    arr[x] = rand.Next(1, 15);
                }
                else
                {
                    arr[x] = rand.Next(1, 20);
                }
            }

            foreach (var item in arr)
                {
                Console.WriteLine(item.ToString());
                }

            int sum = arr.Sum();

            //Console.WriteLine("Sum: " + sum + Environment.NewLine);
        }
    }

Posted 22-Feb-16 3:15am

Keith Lewis

Updated 22-Feb-16 3:26am

Add a Solution

2 solutions

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

OriginalGriff · Accepted Answer · 2016-02-22T03:23:00

First off, move the Random instance outside any method, and make it private:

C#

class GenData
{
    private Random rand = new Random();
    public void GenStats()
    {

That way, it isn't recreated each time you call the method, which can mean repeated values. That's probably what's causing the problem in this case, because the Random constructor uses the system time to "start the sequence" and if you call the GenStats routine quickly in succession, the time doesn't change between constructor calls because your processor is too fast!
Secondly, if you are going to build new GenData instances so quickly, that isn;t going to fix it completely either - so make the Random instance static:

C#

class GenData
{
    private static Random rand = new Random();
    public void GenStats()
    {

Normally, I wouldn't suggest that as it isn't necessarily thread safe, but for this exercise it's probably fine.

Richard MacCutchan · Accepted Answer · 2016-02-22T03:26:00

Solution 2

You need to seed the random generator so it starts at a different value each time. Using the clock time in milliseconds is a useful way of doing it. See Random Constructor (Int32) (System)[^].

Posted 22-Feb-16 3:26am

Richard MacCutchan

Comments

Keith Lewis 22-Feb-16 10:15am

Thankyou, I'll do some reading!