How to make a random number random in C#

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Random ranNum = new Random();

string colorName= "pic" + arrayColors[ranNum.Next(0, 6)];

I tried this code in ASP.NET but in a for loop but the random number seems to stay the same for each loop. How can I make it different for each loop?

Posted 11-Feb-13 21:00pm

GreenKhan

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Jibesh 12-Feb-13 3:03am

where you created the ranNum instance inside loop? try to define it outside loop and use the ranNum.Next inside the loop to get the random number

GreenKhan 12-Feb-13 3:05am

Read my mind, I just tried that as you said. And yes you are correct it worked! :) Thanks!

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OriginalGriff · Accepted Answer · 2013-02-11T21:09:00

The problem is generally that you are creating a new instance of the Random class each time - when you do this, it is initialised from the system clock, and if you create them close together you will get the same "random" sequence each time.
To avoid that, declare your Random object at class level:

C#

private Random ranNum = new Random();

and use the same instance each time you want a new random number.

Mehdi Gholam · Accepted Answer · 2013-02-11T21:05:00

Solution 1

Random takes a seed value which will mix up the start point:

C#

Random r = = new Random(new System.DateTime().Millisecond);

Posted 11-Feb-13 21:05pm

Mehdi Gholam

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Thomas Daniels 12-Feb-13 3:09am

Hi,

I don't think this will make any difference. According to my decompiler, if you create an instance of the Random class, then the seed value is Environment.TickCount. So the start point is already mixed up.

GreenKhan · Accepted Answer · 2013-02-11T21:10:00

As Jibesh said, put

C#

Random ranNum = new Random();

outside the for loop

and this inside

C#

string colorName= "pic" + arrayColors[ranNum.Next(0, 6)];

--------------------------------
CODE
------------------------------------

C#

Random ranNum = new Random();

for (i = 0;i<10;i++){

string colorName= "pic" + arrayColors[ranNum.Next(0, 6)];
}

[Edit]Code blocks added[/Edit]

How to make a random number random in C#

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