Using Randomize() before Rnd() in VB.NET

Question

I have previously been told that I should always use Randomize() before I use Rnd() in a VB.NET application. Yet, it always seems to work fine with

Answer 1

In Visual Basic, Rnd() uses a mathematical operation to produce the next "random" number. Because the actual operation is known, given a specific value, you can predict the next value. However, given an arbitray start value the numbers have good distribution - these are "pseudo-random" numbers.

To keep Rnd() from startng at a predictable number (and hence giving the same sequence of "random" numbers every time), Randomize() should be called to use the machine clock to set the initial value (called a seed).

(In the .NET world, I'd use System.Random instead if you can.)