SharePoint Visual Web Part generate random number unique number every page refresh

I am developing a visual web part for SharePoint 2013.

I have a function that is generating random number that will be used as index to take random item from a collection. I am using below code to generate the random number:

Random randommizer = new Random();
int randomNumber = randommizer.Next(0, allObjects.Count);

I need to have unique random number generated in every page refresh(no postback) even the collection is very small. When the page is refreshed the random value should not be equals to the previous one.

Thanks