Question

Hello i am having some problems generating random numbers with C#
Now i have this function.

public Color getRandomColor()
{
    Color1 = new Random().Next(new Random().Next(0, 100), new Random().Next(200, 255));
    Color2 = new Random().Next(new Random().Next(0, 100), new Random().Next(200, 255));
    Color3 = new Random().Next(new Random().Next(0, 100), new Random().Next(200, 255));
    Color color = Color.FromArgb(Color1, Color2, Color3);
    Console.WriteLine("R: " + Color1 + " G: " + Color2 + " B: " + Color3 + " = " + color.Name);
    return color;
}

Now you might notice that there are ALOT of new Random() there, that is because i want to weed out the probability that it could be a same instance error.

I now run this function 8 times, a couple of times.
Now here are the out puts.

R: 65 G: 65 B: 65 = ff414141
R: 242 G: 242 B: 242 = fff2f2f2
R: 205 G: 205 B: 205 = ffcdcdcd
R: 40 G: 40 B: 40 = ff282828
R: 249 G: 249 B: 249 = fff9f9f9
R: 249 G: 249 B: 249 = fff9f9f9
R: 94 G: 94 B: 94 = ff5e5e5e
R: 186 G: 186 B: 186 = ffbababa

R: 142 G: 142 B: 142 = ff8e8e8e
R: 190 G: 190 B: 190 = ffbebebe
R: 19 G: 19 B: 19 = ff131313
R: 119 G: 119 B: 119 = ff777777
R: 119 G: 119 B: 119 = ff777777
R: 75 G: 75 B: 75 = ff4b4b4b
R: 169 G: 169 B: 169 = ffa9a9a9
R: 127 G: 127 B: 127 = ff7f7f7f

R: 73 G: 73 B: 73 = ff494949
R: 27 G: 27 B: 27 = ff1b1b1b
R: 125 G: 125 B: 125 = ff7d7d7d
R: 212 G: 212 B: 212 = ffd4d4d4
R: 174 G: 174 B: 174 = ffaeaeae
R: 0 G: 0 B: 0 = ff000000
R: 0 G: 0 B: 0 = ff000000
R: 220 G: 220 B: 220 = ffdcdcdc

As you can see this is not so random again, but why dose this happens? and how can i counter it?

Answer 1

You’re creating a new Random for each single value you need.

Try creating a unique Random object and calling the .Next() function multiple times.

public Color getRandomColor()
{
    Random rand = new Random();

    Color1 = rand.Next(rand.Next(0, 100), rand.Next(200, 255));
    Color2 = rand.Next(rand.Next(0, 100), rand.Next(200, 255));
    Color3 = rand.Next(rand.Next(0, 100), rand.Next(200, 255));
    Color color = Color.FromArgb(Color1, Color2, Color3);
    Console.WriteLine("R: " + Color1 + " G: " + Color2 + " B: " + Color3 + " = " + color.Name);
    return color;
}

Taken from MSDN documentation on Random object :

By default, the parameterless constructor of the Random class uses the system clock to generate its seed value, while its parameterized constructor can take an Int32 value based on the number of ticks in the current time. However, because the clock has finite resolution, using the parameterless constructor to create different Random objects in close succession creates random number generators that produce identical sequences of random numbers