Odd behavior in class using Random

Question

Hi all, I am learning C# and built a simple Windows Form app using C# 2010 to experiment with generating random numbers. The app has two buttons and a list box. The code in the button click event is the following:
private void button1_Click(object sender, EventArgs e)
Random rx = new Random();
listBox1.Items.Clear();
for (int i = 0; i<3;i++)
listBox1.Items.Add(rx.NextDouble());
This behaves as expected generating 3 random numbers between 0 and 1.
In the second button click event I have the following code which is similar tothe previous snippet, but uses a function to get the random number:
private void button2_Click(object sender, EventArgs e)
listBox1.Items.Clear();
for (int i = 0; i < 3; i++)
listBox1.Items.Add(GetRnd());
private double GetRnd()
Random rx = new Random();
return rx.NextDouble();
This also works, but I noticed that each time I clicked the button I would generally get the same 2 or 3 random number. After some research and experimentation I concluded that the random # generator was being called so quickly between each iteration that
the same time seed was being used. To solve the problem I moved the Random rx declaration outside of the GetRnd function.
This fixed this issue. I then wanted to see how this function would behave if I placed it in a class:
class clsExample
//Declarations...
Random rx = new Random();
private static double GetRnd()
//Random rx = new Random();
return rx.NextDouble();
This does not work. The source editor places a red squiggly line under the instance name "rx" in the function's return statement. The message provided by the editor: An object reference is required for the non-static field , method or property
'WindowsFormsApplication1.clsExample.rx'.
This error goes away if I instantiate the Random class inside the function, as shown in the snippet above. But if I do this then the randoms numbers repeat. What am I missing? Why does this solution work in the form class and not in the class that I added?
As always, thank you for your help! Saga
Insanity is the prelude to discovery

Answer 1

It seemed to me, from the code you posted previously, that you maybe wanted to use something static. So, rather than remove the static modifier from the method, as Stefan suggested, it might be preferable to add a static modifier to the rx field instead.
// I changed the class name
public class MyRandom
//Declarations...
private static Random rx = new Random();
public static double GetRnd()
return rx.NextDouble();
Then, you'd use it like this:
listBox1.Items.Add(MyRandom.GetRnd());
~~Bonnie DeWitt [C# MVP]
http://geek-goddess-bonnie.blogspot.com