Keith Devens .com - Weblog: Join a NameValueCollection into a querystring in C#

Wednesday, February 13, 2008

Join a NameValueCollection into a querystring in C#

C# is ugly as heck:

private static string JoinNvcToQs(System.Collections.Specialized.NameValueCollection qs){

    return string.Join("&", Array.ConvertAll<string, string>(qs.AllKeys, delegate(string key){

        return string.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(qs[key]));

    }));

}

In Ruby, this would be (essentially):

e = URI.escape

qs.collect{ |k,v| e(k)+"="+e(v) }.join("&")

Permalink | 4 Comments | Tags: C#, Web Development | id 8375

17:03 (utc-6)
edited: 2008-02-14 00:40 (utc-6)

Comments

I think your Ruby code is lacking a .call on the use of the e variable. Maybe you meant:

e = URI.method :escape

qs.collect {|k, v| e.call(k) + '=' + e.call(v)}.join('&')

For one, I don't know how anybody stands using these Java-esque languages. I mean, if you can't get type-inference (the ML-family way), you are better off without static types. Yet even Ruby feels a tad unwieldy (and unsafe) when juxtaposed with a more-functional alternative like SML, OCaml, or (my fave) Haskell.

e = (flip Network.URI.escapeString) reserved

concat $ intersperse "&" [k ++ "=" ++ v | (k, v) <- Data.Map.toList qs]

That is the equivalent in Haskell. I assumed that qs would be a map (corresponds to a pure hashtable). It's pretty.

Yeah I didn't actually execute that Ruby code. I assumed you could take a reference to the method like that, but of course you can't since Ruby lets you call methods without parens. Anyway, the example doesn't change much. Thanks for the correction.

I mean, if you can't get type-inference (the ML-family way), you are better off without static types.

Totally. Like I tried using Array.ConvertAll without the <string, string> on the end, and I got a compiler error saying it couldn't figure out what it was supposed to map to, even though AllKeys returns a string[], the delegate takes a string as a parameter, and the delegate returns a string.

∴ Keith | 14-Feb-2008 12:40am est | http://keithdevens.com/ | #10526

And I swear I would love to use the .NET delegates. A lot. But the syntax is hideous in C#, it was, for long, scarier than C's function pointers. I'm resigned to doing F# if I have to do .NET programming. It's not that often, but still. I'm scarred from having looked C# in the face after a long, long time in the Python/Ruby/Haskell world.

Gustaf Lindqvist (http://lindq.se) wrote:

Well with a lamba expression, this is what I came up with:

private static string JoinNvcToQs(NameValueCollection qs)

{

  return string.Join("&", Array.ConvertAll(qs.AllKeys, key => string.Format("{0}={1}", HttpUtility.UrlEncode(key), HttpUtility.UrlEncode(qs[key]))));

}

∴ Gustaf Lindqvist | 30-Nov-2008 4:38pm est | http://lindq.se | #10982

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