Request.QueryString（）的类型是什么？如何检查它是否为空？

Question

Maybe it's trivial question, but I have no idea what is the type of Request.QueryString() . When I check it with typeof - it says it's Object. How to check which object it is and which property of that object is a string in URL?

I'm doing it server side with language specification <%@ language="javascript"%>

If I've got URL like that: http://127.0.0.1/Kamil/Default.asp?name= then how to check if name is empty? It's not null. I know I can convert Request.QueryString("name") to String and check if it's empty string "", but is it proper way?

Answer 1

The result of Request.Querystring (with no name provided) is a string. The result of Request.Querystring("name") depends on whether "name" is part of the querystring, and if it is, whether it has a value.

So, given the following querystring:

 mypage.asp?A=1&B=

If you read them into variables:

x = Request.Querystring("A")
y = Request.Querystring("B")
z = Request.Querystring("C")

you'll get the following results: x = "1" (a string), y = "" (a blank string), and z = Empty (a special value which will be silently converted to a string or a number depending on how you use it, ie both Empty = "" and Empty = 0 are in some sense true).

Answer 2

The Request collection is an object that inherits IRequestDictionary interface.
In JScript, it's a good practice to use item to get actual value, not the implicit one due to values of the QueryString collection (also Form and ServerVariables ) are IStringList in fact.
You said you know C# so you'll understand the following fictitious QueryString declaration.

var QueryString = new IRequestDictionary<string, IStringList>();

And a few examples how you should check the values in JScript without string conversion.

if(Request.QueryString("name").count==0){
    // parameter does not exist
}

if(Request.QueryString("name").item==undefined){
    // parameter does not exist
}

if(Request.QueryString("name").item!=undefined){
    // parameter exists and may be empty
}

if(Request.QueryString("name").item){
    // parameter exists and non-empty
}