VS 2010 array of structures and get i random

hi
I have to make a struct and fill a array with it.
To fill the arry that is easy
But to get a item random form the array that is also easy.
But to make the ramdon values non repeating that is a lot harder
Ik have to use this
http://msdn.microsoft.com/en-us/libr...em.random.aspx
But the item my only showed once in the listbox NOT TWICE

How can i do that