What's the most efficient way to get a specific parameter from a relative URL string using C#?
For example, how would you get the value of the ACTION parameter from the following relative URL string:
string url = "/page/example?ACTION=data&FOO=test";
I have already tried using:
var myUri = new Uri(url, UriKind.Relative);
String action = HttpUtility.ParseQueryString(myUri.Query).Get("ACTION");
However, I get the following error:
This operation is not supported for a relative URI.
int idx = url.IndexOf('?');
string query = idx >= 0 ? url.Substring(idx) : "";
HttpUtility.ParseQueryString(query).Get("ACTION");
While many of the URI operations are unavailable for UriKind.Relative (for whatever reason), you can build a fully qualified URI through one of the overloads that takes in a Base URI
Here's an example from the docs on Uri.Query:
Uri baseUri = new Uri ("http://www.contoso.com/");
Uri myUri = new Uri (baseUri, "catalog/shownew.htm?date=today");
Console.WriteLine(myUri.Query); // date=today
You can also get the current base from HttpContext.Current.Request.Url or even just create a mock URI base with "http://localhost" if all you care about is the path components.
So either of the following approaches should also return the QueryString from a relative path:
var path = "catalog/shownew.htm?date=today"
var query1 = new Uri(HttpContext.Current.Request.Url, path).Query;
var query2 = new Uri(new Uri("http://localhost"), path).Query;
You can get the query through UriBuilder. This does require the removal of the forward slash from the beginning of the Uri. The query can then be passed to HttpUtility.ParseQueryString to get the desired parameter:
var query = new System.UriBuilder("page/example?ACTION=data&FOO=test").Query;
var parameter = System.Web.HttpUtility.ParseQueryString(query)["ACTION"]; //data
