[C#] Inconsistent form output

1

Hello all,

I am confused by this issue…

Below is some quick code I threw together to test some random number generation and output. The method in the genNum class simply create a string of 9 unique random numbers from 1 to 9 and returns it.

On my button click event it creates 3 separate instances of the genNum class (g1, g2, g3) and then outputs the string to the corresponding textBox (i.e. g1 => textBox1)

Now if I simply run this code without breakpoints, when I click the button it fills the three textbox controls with the same value. I have attached an image of this occurring.
However, if I run it with a breakpoint on, let’s say set on the button click, and step through all the code it runs just fine meaning that in the end it displays 3 separate strings/

This is pretty consistent for me. Every once in awhile (1 out of 1000 times) it will display a separate value in one of the textboxes, usually the last one if I run it without breakpoints. It is 100% fine if I run it with breakpoints.

Here is the code…


namespace TESTingRndGen
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            genNum g1 = new genNum();
            genNum g2 = new genNum();
            genNum g3 = new genNum();

            textBox1.Text = g1.GenerateStringofNumbers();
            textBox2.Text = g2.GenerateStringofNumbers();
            textBox3.Text = g3.GenerateStringofNumbers();
        }
    }

    class genNum
    {
        public string GenerateStringofNumbers()
        {
            Random rnd = new Random();
            string result = "";
            int _randomNumHolder;

            // Generate 9 random numbers
            for(int x = 0; x < 9; x++)
            {
                _randomNumHolder = rnd.Next(1, 10);
                if(x == 0)
                    result = _randomNumHolder.ToString();
                else
                {
                    if(result.Contains(_randomNumHolder.ToString()))
                    {
                        --x;
                    }
                    else
                    {
                        result += _randomNumHolder.ToString();
                    }
                }
            }

            return result;
        }
    }
}

Any insight into this would be greatly appreciated!