This article tells you how to pass variables to an ASP page using the QueryString, and how to access them from that page.
Have you ever seen a URL which looked like
www.example.com/page.asp?mode=1&style=red? Well, this page is being passed variables and their values through the QueryString, here the variables
style are being passed, with values
red respectively. The question mark indicates the start of the query string and the ampersand, &, symbol seperates variable=value assignments.
The page is then able to read these variables and react according to them, for example to display them to the user.
Passing a QueryString to a page
There are two ways to pass a QueryString to a page, the first is to enter it manually, for example:
The above HTML creates a link to a page passing the variable mode with the value
An alternative, and perhaps more useful, way is to use HTML forms. The main thing to remember with forms is that you need to use the GET method to send information via the QueryString, for example:
This code displays a simple HTML form with a text box and a submit button. When the user enters their name and presses submit, the information in the name box is passed to a page called
page.asp (specified in the form’s action attribute) via the QueryString. So, if I entered
admin and pressed submit, the form will call
page.asp?username=admin. Remember that
username was what we entered as the text input’s name attribute.
Accessing a QueryString element in ASP
In ASP, all the information passed via the QueryString is held in the
Request.QueryString collection. To access an item, type
varName is the name of the variable in the QueryString.
To demonstrate, let’s create page.asp to process the information from the form above:
So now, me typing in
admin and pressing submit will generate the reply:
Listing the contents of Request.QueryString
Should you wish to find out everything that’s in the QueryString, you can do so with the following code which displays the variables next to their values in a table:
This article showed you how to pass information between pages with the QueryString, and a use which allows you to add some increased interactivity. There are a lot of other uses, for example selecting which section of a site to display based on a variable in the QueryString, and processing form data.