While it may seem that this is a standard hidden field, there is much more behind-the-scenes going on that one may think. The HiddenField works well in conjunction with the HiddenFieldManager, a topic discussed on the previous page.
Some of the server-side properties include:
Key - A unique key that can be used to denote that hidden field's value. The key can be used in conjunction with the HiddenFieldManager to extract a range of hidden fields with the same key. Think of a client-side version of the DataKeys collection of the
GridView; using this, you can have the HiddenFieldManager extract all of the hidden fields defined within the GridView, which you may have bound to that hidden field a key to keep track of.