Encrypt QueryString parameters in a GridView Hyperlink column

I am using ASP.NET with C#

I have a Hyperlink column in GridView ,, when I click that column, I pass two parameters ,
one  parameter is related to unique ID and another is constant for that gird.
<asp:HyperLinkField DataNavigateUrlFields="pid" HeaderText="Pt Name: click for item entry"  DataNavigateUrlFormatString="billingitemsentry.aspx?pid={0}&type=mhc"    DataTextField="pname" />

Now when I click, the pname, it is going to the destination page and doing the required things.
I wish to encrypt the DataNavigateUrlFormatString
How should the code for encryption and decryption in the destination page
I am attaching the relevant aspx page
PLEASE DO NOT REFER ME TO OTHER LINKS. PLEASE GIVE CODE DIRECTLY USING THE INFORMATION IN THE ATTACHED FILE
billinghomepage.aspx