The Query string collection is a name / value collection, which assembled from the values after the ? in a url.

http://example.com?id=1&Sessionid=1000001

The query string collection in this case will have two name/values pairs in it.
Id=1
Sessionid=1000001

Reference:
Request.QueryString Collection [msdn.microsoft.com]

The Simple thing is html addresses use QueryString property to pass values between pages.In ASP.NET QueryString is passing variables content between pages in ASP.NET.

USE this QueryString property of ”Request Object”