Easiest way to parse "querystring" formatted data

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.

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.

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();