Reputation: 12676

Get URL parameters from a string in .NET

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?

Upvotes: 358

Answers (19)

M Hassaan

Reputation: 1

I am using this code string ID = Request.QueryString["ID"];

Upvotes: 0

Vinod Srivastav

Reputation: 4253

The easiest construct I can think of without any specific dependency looks like

public Dictionary<string,string> Query(Uri queryString)
{
    return queryString.Query.Replace("?","").Split('&').ToDictionary(x=>x.Split('=')[0],x=>x.Split('=')[1]);
}

So for the url

var url = new Uri("http://domain.test/Default.aspx?var1=true&var2=test&var3=3");
Query(url).Dump();

it gives

and the parameters can be accessed as

Query(url)["var1"];
Query(url)["var2"];
Query(url)["var3"];

Upvotes: 0

Jamal Salman

Reputation: 367

If you're in the context of an HttpRequest and using ASPNET core, it can be as simple as Request.Query["paramName"]

I'm not sure when this was added though.

Upvotes: 0

Jamalien

Reputation: 41

In .NET 7

var uri = new Uri("http://example.com/?var1=true&var2=test&var3=3");
var query = HttpUtility.ParseQueryString(uri.Query);
var var1 = query.Get("var1");

Upvotes: 4

John

Reputation: 6278

Here is a sample that mentions what dll to include

var testUrl = "https://www.google.com/?q=foo";

var data = new Uri(testUrl);

// Add a reference to System.Web.dll
var args = System.Web.HttpUtility.ParseQueryString(data.Query);

args.Set("q", "my search term");

var nextUrl = $"{data.Scheme}://{data.Host}{data.LocalPath}?{args.ToString()}";

Upvotes: 2

Amintabar

Reputation: 2266

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

Uri myUri = new Uri("http://www.example.com?param1=good&param2=bad");
var params = myUri.ParseQueryString();
var specific = myUri.ParseQueryString().Get("param1");
var paramByIndex = myUri.ParseQueryString().Get(2);

You can find more from here: https://learn.microsoft.com/en-us/dotnet/api/system.uri?view=net-5.0

Upvotes: 7

Alamakanambra

Reputation: 7891

Easiest way how to get value of know the param name:

using System.Linq;
string loc = "https://localhost:5000/path?desiredparam=that_value&anotherParam=whatever";

var c = loc.Split("desiredparam=").Last().Split("&").First();//that_value

Upvotes: -1

Spirit

Reputation: 61

Single line LINQ solution:

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

Upvotes: 2

Tom Ritter

Reputation: 101400

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

Upvotes: 17

Indy411

Reputation: 3776

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
        }

Upvotes: 0

Ralle12

Reputation: 15

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();
        }

Upvotes: 0

David

Reputation: 34573

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.

Upvotes: 2

Mo Gauvin

Reputation: 169

@Andrew and @CZFox

I had the same bug and found the cause to be that parameter one is in fact: http://www.example.com?param1 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 = "http://www.example.com?param1=good&param2=bad";
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" );`

Upvotes: 16

alsed42

Reputation: 1216

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. http://test/test.html?empty= 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("http://test/test.html", new Dictionary<string, string>());
        DecodeQueryParametersTest("http://test/test.html?", new Dictionary<string, string>());
        DecodeQueryParametersTest("http://test/test.html?key=bla/blub.xml", new Dictionary<string, string> { { "key", "bla/blub.xml" } });
        DecodeQueryParametersTest("http://test/test.html?eins=1&zwei=2", new Dictionary<string, string> { { "eins", "1" }, { "zwei", "2" } });
        DecodeQueryParametersTest("http://test/test.html?empty", new Dictionary<string, string> { { "empty", "" } });
        DecodeQueryParametersTest("http://test/test.html?empty=", new Dictionary<string, string> { { "empty", "" } });
        DecodeQueryParametersTest("http://test/test.html?key=1&", new Dictionary<string, string> { { "key", "1" } });
        DecodeQueryParametersTest("http://test/test.html?key=value?&b=c", new Dictionary<string, string> { { "key", "value?" }, { "b", "c" } });
        DecodeQueryParametersTest("http://test/test.html?key=value=what", new Dictionary<string, string> { { "key", "value=what" } });
        DecodeQueryParametersTest("http://www.google.com/search?q=energy+edge&rls=com.microsoft:en-au&ie=UTF-8&oe=UTF-8&startIndex=&startPage=1%22",
            new Dictionary<string, string>
            {
                { "q", "energy+edge" },
                { "rls", "com.microsoft:en-au" },
                { "ie", "UTF-8" },
                { "oe", "UTF-8" },
                { "startIndex", "" },
                { "startPage", "1%22" },
            });
        DecodeQueryParametersTest("http://test/test.html?key=value;key=anotherValue", 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);
        }
    }
}

Upvotes: 45

Fandango68

Reputation: 4898

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;
        }

Upvotes: 3

CZFox

Reputation: 9275

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

Uri myUri = new Uri("http://www.example.com?param1=good&param2=bad");
string param1 = HttpUtility.ParseQueryString(myUri.Query).Get("param1");

Check documentation at http://msdn.microsoft.com/en-us/library/ms150046.aspx

Upvotes: 664

Erhan Demirci

Reputation: 4209

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");

Upvotes: 0

tomsv

Reputation: 7277

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");

Upvotes: 5

Sergej Andrejev

Reputation: 9413

This is probably what you want

var uri = new Uri("http://domain.test/Default.aspx?var1=true&var2=test&var3=3");
var query = HttpUtility.ParseQueryString(uri.Query);

var var2 = query.Get("var2");

Upvotes: 64

Get URL parameters from a string in .NET

Answers (19)

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