The QueryString collection retrieves the values of the variables in the HTTP query string. The HTTP query string is specified by the values following the question mark (?). Several different processes can generate a query string. For example, the anchor tag
<A HREF= "example?string=this is a sample">string sample</A>
generates a variable named string with the value "this is a sample". Query strings are also generated by sending a form, or by a user typing a query into the address box of their browser.
The QueryString collection is a parsed version of the QUERY_STRING variable in the ServerVariables collection. It enables you to retrieve the QUERY_STRING variables by name. The value of Request.QueryString(parameter) is an array of all of the values of parameter that occur in QUERY_STRING. You can determine the number of values of a parameter by calling Request.QueryString(parameter).Count. If a variable does not have multiple data sets associated with it, the count is 1. If the variable is not found, the count is 0.
To reference a QueryString variable in one of multiple data sets, you specify a value for index. The index parameter may be any value between 1 and Request.QueryString(variable).Count. If you reference one of multiple QueryString variables without specifying a value for index, the data is returned as a comma-delimited string.
When you use parameters with Request.QueryString, the server parses the parameters sent to the request and returns the specified data. If your application requires unparsed QueryString data, you can retrieve it by calling Request.QueryString without any parameters.
You can use an iterator to loop through all the data values in a query string. For example, if the following request is sent
Names.asp contained the following script,
---NAMES.ASP--- <% For Each item In Request.QueryString("Q") Response.Write item & "<BR>" Next %>
Names.asp would display the following.
The preceding script could also have been written using Count.
<% For I = 1 To Request.QueryString("Q").Count Response.Write Request.QueryString("Q")(I) & "<BR>" Next %>
The client request
results in the following QUERY_STRING value.
The QueryString collection would then contain two members,
age. You can then use the following script.
Welcome, <%= Request.QueryString("name") %>. Your age is <%= Request.QueryString("age") %>.
The output would be
Welcome, Fred. Your age is 22.
If the following script is used
The unparsed query string is: <%=Request.QueryString %>
The output would be
The unparsed query string is: name=fred&age=22
ClientCertificate, Cookies, Form, ServerVariables