Outputing a manipulated QueryString in c#

Question

Using the following code I get a nice formatted string:

Request.QueryString.ToString

Gives me something like: &hello=world&microsoft=sucks

But when I use this code to clone the collection to another object (of the same type) I get the Type() back from the ToString() method instead.

System.Collections.Specialized.NameValueCollection variables = new System.Collections.Specialized.NameValueCollection(Request.QueryString);
if (!string.IsNullOrEmpty(variables["sid"]))
    variables.Remove("sid");
Response.Write(variables.ToString());

Is there a tidier way to output it rather than looking and building the string manually?

Answer 1

Why do you want to copy the QueryString collection into a new NameValueCollection?

    if (!string.IsNullOrEmpty(Request.QueryString["sid"]))
        Request.QueryString.Remove("sid");

Yes indeed, i am wrong, it is read only. So the essence is to use the Remove Method on your NameValuecollection:

System.Collections.Specialized.NameValueCollection variables = new System.Collections.Specialized.NameValueCollection(Request.QueryString);
if (!string.IsNullOrEmpty(variables["sid"]))
    variables.Remove("sid");

Answer 2

Request.QueryString actually return a HttpValueCollection object (which unfortuately, is internal to System.Web so you can't you it).

Nevertheless, HttpValueCollection is derived from NameValueCollection, and it's Remove() method remains intact, so you should be able to call Request.QueryString.Remove("sid");

Answer 3

Because it is actually a special NVC that is of type HTTPValueCollection. So when you call .ToString on it, it knows how to format it correctly.

Answer 4

You can also use Reflector to extract the HttpValueCollection class into your own, and use it then.

Answer 5

If you don't absolutely need a NameValueCollection, A dictionary offers a lot of the same semantics:

var variables = Request.QueryString.OfType<DictionaryEntry>()
    .Where(entry => entry.Key != "sid")
    .ToDictionary(entry => entry.Key, entry => entry.Value);

Answer 6

HttpValueCollection is internal, but you can use "var" to declare it without extract it with reflector.

var query = HttpUtility.ParseQueryString(Request.Url.Query);
query["Lang"] = myLanguage; // Add or replace param
string myNewUrl = Request.Url.AbsolutePath + "?" + query;