I've got a string in .NET which is actually a URL. I want an easy way to get the value from a particular parameter.

Normally, I'd just use Request.Params["theThingIWant"], but this string isn't from the request. I can create a new Uri item like so:

Uri myUri = new Uri(TheStringUrlIWantMyValueFrom);

I can use myUri.Query to get the query string...but then I apparently have to find some regexy way of splitting it up.

Am I missing something obvious, or is there no built in way to do this short of creating a regex of some kind, etc?

15 Answers

Use static ParseQueryString method of System.Web.HttpUtility class that returns NameValueCollection.

Uri myUri = new Uri("");
string param1 = HttpUtility.ParseQueryString(myUri.Query).Get("param1");

Check documentation at

7

This is probably what you want

var uri = new Uri("");
var query = HttpUtility.ParseQueryString(uri.Query);
var var2 = query.Get("var2");

1

Here's another alternative if, for any reason, you can't or don't want to use HttpUtility.ParseQueryString().

This is built to be somewhat tolerant to "malformed" query strings, i.e. becomes a parameter with an empty value. The caller can verify the parameters if needed.

public static class UriHelper
{ public static Dictionary<string, string> DecodeQueryParameters(this Uri uri) { if (uri == null) throw new ArgumentNullException("uri"); if (uri.Query.Length == 0) return new Dictionary<string, string>(); return uri.Query.TrimStart('?') .Split(new[] { '&', ';' }, StringSplitOptions.RemoveEmptyEntries) .Select(parameter => parameter.Split(new[] { '=' }, StringSplitOptions.RemoveEmptyEntries)) .GroupBy(parts => parts[0], parts => parts.Length > 2 ? string.Join("=", parts, 1, parts.Length - 1) : (parts.Length > 1 ? parts[1] : "")) .ToDictionary(grouping => grouping.Key, grouping => string.Join(",", grouping)); }
}

Test

[TestClass]
public class UriHelperTest
{ [TestMethod] public void DecodeQueryParameters() { DecodeQueryParametersTest("", new Dictionary<string, string>()); DecodeQueryParametersTest("", new Dictionary<string, string>()); DecodeQueryParametersTest("", new Dictionary<string, string> { { "key", "bla/blub.xml" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "eins", "1" }, { "zwei", "2" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "empty", "" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "empty", "" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "key", "1" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "key", "value?" }, { "b", "c" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "key", "value=what" } }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "q", "energy+edge" }, { "rls", "com.microsoft:en-au" }, { "ie", "UTF-8" }, { "oe", "UTF-8" }, { "startIndex", "" }, { "startPage", "1%22" }, }); DecodeQueryParametersTest("", new Dictionary<string, string> { { "key", "value,anotherValue" } }); } private static void DecodeQueryParametersTest(string uri, Dictionary<string, string> expected) { Dictionary<string, string> parameters = new Uri(uri).DecodeQueryParameters(); Assert.AreEqual(expected.Count, parameters.Count, "Wrong parameter count. Uri: {0}", uri); foreach (var key in expected.Keys) { Assert.IsTrue(parameters.ContainsKey(key), "Missing parameter key {0}. Uri: {1}", key, uri); Assert.AreEqual(expected[key], parameters[key], "Wrong parameter value for {0}. Uri: {1}", parameters[key], uri); } }
}

3

Looks like you should loop over the values of myUri.Query and parse it from there.

 string desiredValue; foreach(string item in myUri.Query.Split('&')) { string[] parts = item.Replace("?", "").Split('='); if(parts[0] == "desiredKey") { desiredValue = parts[1]; break; } }

I wouldn't use this code without testing it on a bunch of malformed URLs however. It might break on some/all of these:

• hello.html?
• hello.html?valuelesskey
• hello.html?key=value=hi
• hello.html?hi=value?&b=c
• etc

@Andrew and @CZFox

I had the same bug and found the cause to be that parameter one is in fact: and not param1 which is what one would expect.

By removing all characters before and including the question mark fixes this problem. So in essence the HttpUtility.ParseQueryString function only requires a valid query string parameter containing only characters after the question mark as in:

HttpUtility.ParseQueryString ( "param1=good&param2=bad" )

My workaround:

string RawUrl = "";
int index = RawUrl.IndexOf ( "?" );
if ( index > 0 ) RawUrl = RawUrl.Substring ( index ).Remove ( 0, 1 );
Uri myUri = new Uri( RawUrl, UriKind.RelativeOrAbsolute);
string param1 = HttpUtility.ParseQueryString( myUri.Query ).Get( "param1" );`

4

You can just use the Uri to get the list of the query strings or find a specific parameter.

Uri myUri = new Uri("");
var params = myUri.ParseQueryString();
var specific = myUri.ParseQueryString().Get("spesific");
var paramByIndex = = myUri.ParseQueryString().Get(1);

You can find more from here:

You can use the following workaround for it to work with the first parameter too:

var param1 = HttpUtility.ParseQueryString(url.Substring( new []{0, url.IndexOf('?')}.Max() )).Get("param1");

Or if you don't know the URL (so as to avoid hardcoding, use the AbsoluteUri

Example ...

 //get the full URL Uri myUri = new Uri(Request.Url.AbsoluteUri); //get any parameters string strStatus = HttpUtility.ParseQueryString(myUri.Query).Get("status"); string strMsg = HttpUtility.ParseQueryString(myUri.Query).Get("message"); switch (strStatus.ToUpper()) { case "OK": webMessageBox.Show("EMAILS SENT!"); break; case "ER": webMessageBox.Show("EMAILS SENT, BUT ... " + strMsg); break; }

Use .NET Reflector to view the FillFromString method of System.Web.HttpValueCollection. That gives you the code that ASP.NET is using to fill the Request.QueryString collection.

Single line LINQ solution:

Dictionary<string, string> ParseQueryString(string query)
{ return query.Replace("?", "").Split('&').ToDictionary(pair => pair.Split('=').First(), pair => pair.Split('=').Last());
}

if you want in get your QueryString on Default page .Default page means your current page url . you can try this code :

string paramIl = HttpUtility.ParseQueryString(this.ClientQueryString).Get("city");

This is actually very simple, and that worked for me :)

 if (id == "DK") { string longurl = "selectServer.aspx?country="; var uriBuilder = new UriBuilder(longurl); var query = HttpUtility.ParseQueryString(uriBuilder.Query); query["country"] = "DK"; uriBuilder.Query = query.ToString(); longurl = uriBuilder.ToString(); } 

For anyone who wants to loop through all query strings from a string

 foreach (var item in new Uri(urlString).Query.TrimStart('?').Split('&')) { var subStrings = item.Split('='); var key = subStrings[0]; var value = subStrings[1]; // do something with values }

HttpContext.Current.Request.QueryString.Get("id");

1

I used it and it run perfectly

<%=Request.QueryString["id"] %>

1

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