Question

Hi
i want random no. of questions. For that i used random function in asp.net but questions gets repeating.
How i can get non repeated questions.
C#.
Thank you.

Answer 1

The problem with Random is very often the following:

The following code will very often return a very ‘non-random’ sequence of numbers

        for(int j = 0; j<100; j++)
        {
            Random rnd = new Random();      
            int i = rnd.Next(1, 5);
            Console.WriteLine(i);
        }

Whereas the following will create a more randomized distribution of numbers:

        Random rnd = new Random(); 
        for(int j = 0; j<100; j++)
        {

            int i = rnd.Next(1, 5);
            Console.WriteLine(i);
        }

A different approach to generating a random number could be achieved using Linq:

var randomNumber = Enumerable.Range(1, 10).OrderBy(g => Guid.NewGuid()).First();

This method first creates a list of numbers (in this example from 1 to 10), and then orders that list by creating a Guid. This shuffles the list so that the First() will be kind of random. I often rely on this method to get a random number instead of using the Random-class.

UPDATE

Let’s say you want 10 unique random numbers from a list of 100 random numbers. Using the linq-expression you would do:

List<int> tenRandomNumbers = Enumerable.Range(1, 100).OrderBy(g => Guid.NewGuid()).Take(10);

Now you should be able to go through the list of tenRandomNumbers .. They should be unique and random.

UPDATE 2

Take a look at this explanation of the .Take(int) method:
http://msdn.microsoft.com/en-us/vcsharp/aa336757#TakeSimple

The code above will return a list of 10 numbers selected randomly from a collection of 100 numbers. What you want to do next is simply:

foreach(int i in tenRandomNumbers){
   // code to fetch your question based on int i
}

Hope this helps