Easiest way to parse "querystring" formatted data

Question

With the following code:

string q = "userID=16555&gameID=60&score=4542.122&time=343114";

What would be the easiest way to parse the values, preferably without writing my own parser? I'm looking for something with the same functionality as Request.querystring["gameID"].

score 87 · Answer 1 · edited Jan 02 '16 at 14:50

87

Pretty easy... Use the HttpUtility.ParseQueryString method.

Untested, but this should work:

var qs = "userID=16555&gameID=60&score=4542.122&time=343114";
var parsed = HttpUtility.ParseQueryString(qs);
var userId = parsed["userID"]; 
//  ^^^^^^ Should be "16555".  Note this will be a string of course.

edited Jan 02 '16 at 14:50

Sergey Vyacheslavovich Brunov

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answered Aug 14 '12 at 16:43

Chris Shain

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1

Thanks! Looks good, I'm having trouble decoding the horrible example they provided on the MSDN page though, once I have `var q = HttpUtility.ParseQueryString("?userID=16555&gameID=60&score=4542.122&time=343114");` how do I retrieve a specific value? – Tom Gullen Aug 14 '12 at 16:46
1

I can't find System.Net.HttpUtility net Core 1.0 framework – Aakash Jul 18 '16 at 04:50
1

Seems like they removed it. Reference the answer here for a solution: http://stackoverflow.com/questions/29992848/parse-and-modify-a-query-string-in-net-core – Chris Shain Jul 18 '16 at 11:52
The [Nancy](http://nancyfx.org/) library also includes `Nancy.Helpers.HttpUtility.ParseQueryString`. – TrueWill Oct 06 '16 at 21:55
Note that `ParseQueryString` fails is there is more than 1024 key-value pairs in the string. – GSerg Jul 18 '21 at 12:54
@GSerg if you’ve got 1025 keys in a query string, I’d argue that you’ve got bigger problems – Chris Shain Jul 18 '21 at 13:15
@ChrisShain Well, there is e.g. one Paypal API that returns transactions data as a huge url-encoded string of key-value pairs. It easily exceeds 1024. – GSerg Jul 18 '21 at 13:27

Adil · Answer 2 · 2014-11-21T04:27:36.827

23

You can do it with linq like this.

string query = "id=3123123&userId=44423&format=json";

Dictionary<string,string> dicQueryString = 
        query.Split('&')
             .ToDictionary(c => c.Split('=')[0],
                           c => Uri.UnescapeDataString(c.Split('=')[1]));

string userId = dicQueryString["userID"];

Edit

If you can use HttpUtility.ParseQueryString then it will be a lot more straight forward and it wont be case-sensitive as in case of LinQ.

edited Nov 21 '14 at 04:27

answered Aug 14 '12 at 16:51

Adil

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That works in this specific case, but it's not a generic solution because it doesn't do percent-decoding. – Francis Avila Aug 14 '12 at 16:57
Right @Francis Avila, then it will need more modification in query. – Adil Aug 14 '12 at 17:04
2

This is a good solution if you need to parse query strings outside of the System.Web context. – Rick Strahl Sep 06 '14 at 23:13
This preserves case, unlike ParseQueryString. – sirbrialliance Nov 20 '14 at 16:56
7

And what happens when you have a query string like `a=1&a=2&a=3`? That is valid, as is `a=1;a=2;a=3`. Use `HttpUtility.ParseQueryString`. It handles these and other oddities. – Jim Mischel Nov 21 '14 at 05:14
I came here because HttpUtility.ParseQueryString() performed the decoding. this solution here works for me. – kennydust Jul 08 '15 at 07:47
@JimMischel to `.ToLookup` rather than `.ToDictionary` to handle "duplicate keys" – drzaus Aug 27 '15 at 20:58

score 7 · Answer 3 · edited May 23 '17 at 11:46

As has been mentioned in each of the previous answers, if you are in a context where you can add a dependency to the System.Web library, using HttpUtility.ParseQueryString makes sense. (For reference, the relevant source can be found in the Microsoft Reference Source). However, if this is not possible, I would like to propose the following modification to Adil's answer which accounts for many of the concerns addressed in the comments (such as case sensitivity and duplicate keys):

var q = "userID=16555&gameID=60&score=4542.122&time=343114";
var parsed = q.TrimStart('?')
    .Split(new[] { '&' }, StringSplitOptions.RemoveEmptyEntries)
    .Select(k => k.Split('='))
    .Where(k => k.Length == 2)
    .ToLookup(a => a[0], a => Uri.UnescapeDataString(a[1])
      , StringComparer.OrdinalIgnoreCase);
var userId = parsed["userID"].FirstOrDefault();
var time = parsed["TIME"].Select(v => (int?)int.Parse(v)).FirstOrDefault();

Ignores single item arguments, which can sometimes also appear: `arg1&arg2&arg3` — jsuddsjr, Jun 17 '19 at 17:16

score 5 · Answer 4 · edited Dec 14 '17 at 20:24

5

If you want to avoid the dependency on System.Web that is required to use HttpUtility.ParseQueryString, you could use the Uri extension method ParseQueryString found in System.Net.Http.

Note that you have to convert the response body to a valid Uri so that ParseQueryString works.

Please also note in the MSDN document, this method is an extension method for the Uri class, so you need reference the assembly System.Net.Http.Formatting (in System.Net.Http.Formatting.dll). I tried installed it by the nuget package with the name "System.Net.Http.Formatting", and it works fine.

string body = "value1=randomvalue1&value2=randomValue2";

// "http://localhost/query?" is added to the string "body" in order to create a valid Uri.
string urlBody = "http://localhost/query?" + body;
NameValueCollection coll = new Uri(urlBody).ParseQueryString();

edited Dec 14 '17 at 20:24

Qin Chao

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answered Aug 16 '17 at 14:30

Amadeus Sanchez

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Not sure this works...Uri doesn't have a ParseQueryString method attached to it when I try this, my code: var collection = new System.Uri(url).ParseQueryString(); – Trevor Hart Dec 11 '17 at 19:16
@TrevorHart Did you make sure to add a reference to System.Net.Http and to add the System.Net.Http namespace? – Amadeus Sanchez Dec 14 '17 at 16:43
1

I did, I ended up just writing my own parser. – Trevor Hart Dec 14 '17 at 19:01

penguin river · Answer 5 · 2018-11-05T11:41:12.683

4

How is this

using System.Text.RegularExpressions;

// query example
//   "name1=value1&name2=value2&name3=value3"
//   "?name1=value1&name2=value2&name3=value3"
private Dictionary<string, string> ParseQuery(string query)
{
    var dic = new Dictionary<string, string>();
    var reg = new Regex("(?:[?&]|^)([^&]+)=([^&]*)");
    var matches = reg.Matches(query);
    foreach (Match match in matches) {
        dic[match.Groups[1].Value] = Uri.UnescapeDataString(match.Groups[2].Value);
    }
    return dic;
}

edited Nov 05 '18 at 11:41

answered Nov 05 '18 at 11:22

penguin river

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Thanks!! Does it support single item arguments, as metioned by @jsuddsjr 's comment above? _Ignores single item arguments, which can sometimes also appear: `arg1&arg2&arg3`_ – gregn3 Nov 23 '20 at 18:06

score 2 · Answer 6 · answered May 17 '22 at 16:18

2

For .NET Core there is Microsoft.AspNetCore.WebUtilities.QueryHelpers.ParseQuery

var queryString = QueryHelpers.ParseQuery("?param1=value");
var queryParamValue = queryString["param1"];

Code snippet modified from trackjs.com:

answered May 17 '22 at 16:18

bobbyg603

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score 1 · Answer 7 · answered Aug 04 '19 at 22:04

1

System.Net.Http ParseQueryString extension method worked for me. I'm using OData query options and trying to parse out some custom parameters.

options.Request.RequestUri.ParseQueryString();

Seems to give me what I need.

answered Aug 04 '19 at 22:04

MrRobboto

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score 0 · Answer 8 · answered Apr 26 '22 at 14:58

HttpUtility.ParseQueryString will work as long as you are in a web app or don't mind including a dependency on System.Web. Another way to do this is:

// NameValueCollection nameValueCollection = HttpUtility.ParseQueryString(queryString);

NameValueCollection nameValueCollection = new NameValueCollection();
string[] querySegments = queryString.Split('&');
foreach(string segment in querySegments)
{
   string[] parts = segment.Split('=');
   if (parts.Length > 0)
   {
      string key = parts[0].Trim(new char[] { '?', ' ' });
      string val = parts[1].Trim();

      nameValueCollection.Add(key, val);
   }
}

Easiest way to parse "querystring" formatted data

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