How to parse a query string into a NameValueCollection in .NET

Solution 1:

There's a built-in .NET utility for this: HttpUtility.ParseQueryString

// C#
NameValueCollection qscoll = HttpUtility.ParseQueryString(querystring);

' VB.NET
Dim qscoll As NameValueCollection = HttpUtility.ParseQueryString(querystring)

You may need to replace querystring with new Uri(fullUrl).Query.

Solution 2:

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 queryParameters = 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();

      queryParameters.Add(key, val);
   }
}

Solution 3:

A lot of the answers are providing custom examples because of the accepted answer's dependency on System.Web. From the Microsoft.AspNet.WebApi.Client NuGet package there is a UriExtensions.ParseQueryString, method that can also be used:

var uri = new Uri("https://stackoverflow.com/a/22167748?p1=6&p2=7&p3=8");
NameValueCollection query = uri.ParseQueryString();

So if you want to avoid the System.Web dependency and don't want to roll your own, this is a good option.

Solution 4:

I wanted to remove the dependency on System.Web so that I could parse the query string of a ClickOnce deployment, while having the prerequisites limited to the "Client-only Framework Subset".

I liked rp's answer. I added some additional logic.

public static NameValueCollection ParseQueryString(string s)
    {
        NameValueCollection nvc = new NameValueCollection();

        // remove anything other than query string from url
        if(s.Contains("?"))
        {
            s = s.Substring(s.IndexOf('?') + 1);
        }

        foreach (string vp in Regex.Split(s, "&"))
        {
            string[] singlePair = Regex.Split(vp, "=");
            if (singlePair.Length == 2)
            {
                nvc.Add(singlePair[0], singlePair[1]);
            }
            else
            {
                // only one key with no value specified in query string
                nvc.Add(singlePair[0], string.Empty);
            }
        }

        return nvc;
    }

Solution 5:

I needed a function that is a little more versatile than what was provided already when working with OLSC queries.

Values may contain multiple equal signs
Decode encoded characters in both name and value
Capable of running on Client Framework
Capable of running on Mobile Framework.

Here is my solution:

Public Shared Function ParseQueryString(ByVal uri As Uri) As System.Collections.Specialized.NameValueCollection
    Dim result = New System.Collections.Specialized.NameValueCollection(4)
    Dim query = uri.Query
    If Not String.IsNullOrEmpty(query) Then
        Dim pairs = query.Substring(1).Split("&"c)
        For Each pair In pairs
            Dim parts = pair.Split({"="c}, 2)

            Dim name = System.Uri.UnescapeDataString(parts(0))
            Dim value = If(parts.Length = 1, String.Empty,
                System.Uri.UnescapeDataString(parts(1)))

            result.Add(name, value)
        Next
    End If
    Return result
End Function

It may not be a bad idea to tack <Extension()> on that too to add the capability to Uri itself.