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.NET Forum / Languages / C# / April 2008HttpContext.Current.Request.QueryString
Hi if I have a url/query like "localhost?a&b&c=123" then I thought I could get these parameters and values by using NameValueCollection query = HttpContext.Current.Request.QueryString; But if I then try "query.AllKeys" I only get two keys, namely "null" and "c". Is this correct behaviour? Are "a" and "b" considered to be values for a null key - and how do I get them from the collection? Thanks, Peter > Hi > [quoted text clipped - 7 lines] > Is this correct behaviour? Are "a" and "b" considered to be values for > a null key - and how do I get them from the collection? Shouldn't the query string be: "localhost?a=&b=&c=123" ? FB  Signature------------------------------------------------------------------------ Lead developer of LLBLGen Pro, the productive O/R mapper for .NET LLBLGen Pro website: http://www.llblgen.com My .NET blog: http://weblogs.asp.net/fbouma Microsoft MVP (C#) ------------------------------------------------------------------------ > > if I have a url/query like "localhost?a&b&c=123" then I thought I > > could get these parameters and values by using [quoted text clipped - 7 lines] > > Shouldn't the query string be: "localhost?a=&b=&c=123" ? Yes, I think you're right, the query should really look like that. I guess I should ignore any null keys I get from AllKeys (what can I use a null key for anyway?) Thanks, Peter > > > if I have a url/query like "localhost?a&b&c=123" then I thought I > > > could get these parameters and values by using [quoted text clipped - 15 lines] > Thanks, > Peter Who is generating that query string? As Frans mentioned it's wrong. You should have default values for all your parameters, and then just update those with values in the QS. so all you have to do at the most is adding a if (key==null) continue; > > > > if I have a url/query like "localhost?a&b&c=123" then I thought > > > > I could get these parameters and values by using [quoted text clipped - 24 lines] > update those with values in the QS. > so all you have to do at the most is adding a if (key==null) continue; In my program I was using AllKeys, and looping over the keys doing some processing. Unfortunately I did not take account of the fact that a key could be null. A user decided to edit the query string himself, and then we got an exception. I did just like you said, and now check if the key is null before processing it. I can't really see the point in AllKeys returning a null key, but there you go... /Peter It is very common to see querystrings with null key values (e.g., &ua=&bg=1 ) rather than the key not being present. Just take a look at some google searches to see examples of this. -- Peter To be a success, arm yourself with the tools you need and learn how to use them. Site: http://www.eggheadcafe.com http://petesbloggerama.blogspot.com http://ittyurl.net > > > > > if I have a url/query like "localhost?a&b&c=123" then I thought > > > > > I could get these parameters and values by using [quoted text clipped - 39 lines] > > /Peter > It is very common to see querystrings with null key values (e.g., > &ua=&bg=1 ) rather than the key not being present. Just take a look > at some google searches to see examples of this. In your example there are no "null keys". You have a key called "ua" and a key called "bg". The value for ua is empty, and the value for bg is 1. If your query string was "&ua&bg=1" then AllKeys would return two keys: null and "bg". I don't really understand the point of a null key. /Peter There needs to be an equals (=) sign after each key name. -- Peter To be a success, arm yourself with the tools you need and learn how to use them. Site: http://www.eggheadcafe.com http://petesbloggerama.blogspot.com http://ittyurl.net > > It is very common to see querystrings with null key values (e.g., > > &ua=&bg=1 ) rather than the key not being present. Just take a look [quoted text clipped - 11 lines] > > /Peter > There needs to be an equals (=) sign after each key name. Yes indeed. I found that out. But what to do if a user enters the query string in the browser.... It seems strange to me that (1) the browser (internet explorer) sends an "illegal" query string; and (2) the AllKeys property returns a key which is null - using a null key to retrieve a value from the NameValueCollection results in an error of course. /Peter I think it would be pretty rare for a web application that expects a user to be creating their "own" querystrings. You can type whatever gobbledegook you want after a URI in the Address Bar of your browser, and the browser will happily attempt to retrieve the resource for you. Cheers. -- Peter To be a success, arm yourself with the tools you need and learn how to use them. Site: http://www.eggheadcafe.com http://petesbloggerama.blogspot.com http://ittyurl.net > > There needs to be an equals (=) sign after each key name. > [quoted text clipped - 7 lines] > > /Peter > I think it would be pretty rare for a web application that expects a > user to be creating their "own" querystrings. You can type whatever > gobbledegook you want after a URI in the Address Bar of your browser, > and the browser will happily attempt to retrieve the resource for > you. I don't know if we're talking/writing past each other here... but it was never the idea that a user should write parameters in the url in the browser. However, one of our users did (for their own nefarious reasons), and that's when we discovered an error in our program. The user wrote a query like "?a&b&c=123". It could very well be this is an invalid query. The browser though, as you wrote, happily sent this invalid query to our web-app. The web-app received that invalid query, and as part of its normal processing used the AllKeys property of HttpContext.Current.Request.QueryString to loop over all the keys. This caused an unhandled error in our program because we were not aware that a key could be null. We are now aware of this fact, and have corrected our program to not attempt to process any null keys. I am still surprised that AllKeys can return a key which is null, but that's just life I guess :-) Thanks, Peter > > There needs to be an equals (=) sign after each key name. > [quoted text clipped - 7 lines] > > /Peter Hi, Then you are playing with fire, just be ready for a var not to be present, or as in your first post an incorrect QS. > > > There needs to be an equals (=) sign after each key name. > > [quoted text clipped - 12 lines] > Then you are playing with fire, just be ready for a var not to be > present, or as in your first post an incorrect QS. Yes, thanks, we've fixed our application now. I guess QueryString interprets "a" and "b" in "localhost?a&b&c=123" as values which don't have a parameter name. I thought they'd be interpreted as parameter names which don't have any values - but that would be "?a=&b=". I may even use this at some stage if I can't think of a good name for a parameter and I just want to send some values to my web-app. Thanks, Peter Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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