int[] aux
= new int[lista
.Count];
for (int i = 0; i < aux.Length; i++) //For para poner los valores en -1 del vector
aux[i] = -1;
for (int i = 0; i < aux.Length; i++)
{
int num = r.Next(0, aux.Length);
for (int j = 0; j <= i; j++)
{
if (aux[j] == num)
{
num = r.Next(0, aux.Length);
j = -1;
}
}
aux[i] = num;
}