Create a uniqe random number

I want to create a random unique numbers therefore I wrote 2 codes but i'm wondering if those codes will match my needs .

CODE 1:

Random rand = new Random((Guid.NewGuid().GetHashCode()));
int numIterations = 0;
numIterations = rand.Next(100000, 999999);
return numIterations.ToString();

CODE 2:

Random rand = new Random((int)DateTime.Now.Ticks);
int numIterations = 0;
numIterations = rand.Next(100000, 999999);
return numIterations.ToString();

please help me .