C# System.Random Next comes out sorted

I am trying to access random elements from an array, but the Random generator that I am using keeps on giving me numbers in order like so:

The numbers will always come out sequenced, never completely random (ie. the next number is always greater until the max is reached, then starts from low numbers again). This can be incremental or decremental as well.

I am using a seeded Random object and Random.Next(-100, 100). This is not the same as the behaviour demonstrated on the MSDN Random.Next page

All I can think of is that the version of .Net packaged with Unity does not have the most recent Random? Any solutions to this confusion?