method for shuffling elements of an array

Question

Hello my friends.

I need a method which takes an array of element than returns it with elements which are in randomized order.

For that purpose I developed following method

        string[] shuffle(string[] a)

        {

       

         

             for (int i = 0; i < a.Length; i++)

             {

                 string tmp = a[i];

                 int randomnumber = rnd.Next(i, a.Length);

                 a[i] = a[randomnumber];

                 a[randomnumber] = tmp;

             

             }

             return a;

            

        }

but it returns sometimes the duplicate elements, which is wrong.

I need help.