What does this ASP representation mean?

I clean my asp.net web form and it always submits views like this:

<input type="hidden" name="__VIEWSTATE" value="/wEXAQUDX19QDwUNZnJtQ291cnNlSW5mbw8GblQKzmHhzYgCAw==">

When I decodes it into the View Take State decoder's , I get this object: System.Collections.Hashtable.

The exact value of __VIEWSTATE is changing, but it aldasy decodes the object System.Collections.Hashtable.

What's going on here? Why is the viewstate value changed but always decoded?