How to parse a query string into a NameValueCollec

问题:

I would like to parse a string such as p1=6&p2=7&p3=8 into a NameValueCollection.

What is the most elegant way of doing this when you don\'t have access to the Page.Request object?

回答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.

回答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);
   }
}

回答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.

回答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;
    }

回答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.

回答6:

To do this without System.Web, without writing it yourself, and without additional NuGet packages:

1. Add a reference to System.Net.Http.Formatting
2. Add using System.Net.Http;

3. Use this code:

   new Uri(uri).ParseQueryString()
   

https://msdn.microsoft.com/en-us/library/system.net.http.uriextensions(v=vs.118).aspx

回答7:

    private void button1_Click( object sender, EventArgs e )
    {
        string s = @\"p1=6&p2=7&p3=8\";
        NameValueCollection nvc = new NameValueCollection();

        foreach ( string vp in Regex.Split( s, \"&\" ) )
        {
            string[] singlePair = Regex.Split( vp, \"=\" );
            if ( singlePair.Length == 2 )
            {
                nvc.Add( singlePair[ 0 ], singlePair[ 1 ] );    
            }    
        }
    }

回答8:

I just realized that Web API Client has a ParseQueryString extension method that works on a Uri and returns a HttpValueCollection:

var parameters = uri.ParseQueryString();
string foo = parameters[\"foo\"];

回答9:

If you want to avoid the dependency on System.Web that is required to use HttpUtility.ParseQueryString, you could use the Uri extension method ParseQueryString found in System.Net.Http.

Make sure to add a reference (if you haven\'t already) to System.Net.Http in your project.

Note that you have to convert the response body to a valid Uri so that ParseQueryString (in System.Net.Http)works.

string body = \"value1=randomvalue1&value2=randomValue2\";

// \"http://localhost/query?\" is added to the string \"body\" in order to create a valid Uri.
string urlBody = \"http://localhost/query?\" + body;
NameValueCollection coll = new Uri(urlBody).ParseQueryString();

回答10:

Just access Request.QueryString. AllKeys mentioned as another answer just gets you an array of keys.

回答11:

HttpUtility.ParseQueryString(Request.Url.Query) return is HttpValueCollection (internal class). It inherits from NameValueCollection.

    var qs = HttpUtility.ParseQueryString(Request.Url.Query);
    qs.Remove(\"foo\"); 

    string url = \"~/Default.aspx\"; 
    if (qs.Count > 0)
       url = url + \"?\" + qs.ToString();

    Response.Redirect(url); 

回答12:

If you don\'t want the System.Web dependency, just paste this source code from HttpUtility class.

I just whipped this together from the source code of Mono. It contains the HttpUtility and all it\'s dependencies (like IHtmlString, Helpers, HttpEncoder, HttpQSCollection).

Then use HttpUtility.ParseQueryString.

https://gist.github.com/bjorn-ali-goransson/b04a7c44808bb2de8cca3fc9a3762f9c

回答13:

Since everyone seems to be pasting his solution.. here\'s mine :-) I needed this from within a class library without System.Web to fetch id parameters from stored hyperlinks.

Thought I\'d share because I find this solution faster and better looking.

public static class Statics
    public static Dictionary<string, string> QueryParse(string url)
    {
        Dictionary<string, string> qDict = new Dictionary<string, string>();
        foreach (string qPair in url.Substring(url.IndexOf(\'?\') + 1).Split(\'&\'))
        {
            string[] qVal = qPair.Split(\'=\');
            qDict.Add(qVal[0], Uri.UnescapeDataString(qVal[1]));
        }
        return qDict;
    }

    public static string QueryGet(string url, string param)
    {
        var qDict = QueryParse(url);
        return qDict[param];
    }
}

Usage:

Statics.QueryGet(url, \"id\")

回答14:

Hit up Request.QueryString.Keys for a NameValueCollection of all query string parameters.

回答15:

To get all Querystring values try this:

    Dim qscoll As NameValueCollection = HttpUtility.ParseQueryString(querystring)

Dim sb As New StringBuilder(\"<br />\")
For Each s As String In qscoll.AllKeys

  Response.Write(s & \" - \" & qscoll(s) & \"<br />\")

Next s

回答16:

        var q = Request.QueryString;
        NameValueCollection qscoll = HttpUtility.ParseQueryString(q.ToString());

回答17:

I translate to C# version of josh-brown in VB

private System.Collections.Specialized.NameValueCollection ParseQueryString(Uri uri)
{
    var result = new System.Collections.Specialized.NameValueCollection(4);
    var query = uri.Query;
    if (!String.IsNullOrEmpty(query))
    {
        var pairs = query.Substring(1).Split(\"&\".ToCharArray());
        foreach (var pair in pairs)
        {
            var parts = pair.Split(\"=\".ToCharArray(), 2);
            var name = System.Uri.UnescapeDataString(parts[0]);
            var value = (parts.Length == 1) ? String.Empty : System.Uri.UnescapeDataString(parts[1]);
            result.Add(name, value);
        }
    }
    return result;
}

回答18:

This is my code, I think it\'s very useful:

public String GetQueryString(string ItemToRemoveOrInsert = null, string InsertValue = null )
{
    System.Collections.Specialized.NameValueCollection filtered = new System.Collections.Specialized.NameValueCollection(Request.QueryString);
    if (ItemToRemoveOrInsert != null)
    {
        filtered.Remove(ItemToRemoveOrInsert);
        if (!string.IsNullOrWhiteSpace(InsertValue))
        {
            filtered.Add(ItemToRemoveOrInsert, InsertValue);
        }
    }

    string StrQr = string.Join(\"&\", filtered.AllKeys.Select(key => key + \"=\" + filtered[key]).ToArray());
    if (!string.IsNullOrWhiteSpace(StrQr)){
        StrQr=\"?\" + StrQr;
    }

    return StrQr;
}