HttpUtility.ParseQueryString Method (String)

Parses a query string into a NameValueCollection using UTF8 encoding.

Namespace: System.Web
Assembly: System.Web (in system.web.dll)

public static NameValueCollection ParseQueryString (
	string query
public static NameValueCollection ParseQueryString (
	String query
public static function ParseQueryString (
	query : String
) : NameValueCollection
Not applicable.



The query string to parse.

Return Value

A NameValueCollection of query parameters and values.

Exception typeCondition


query is a null reference (Nothing in Visual Basic).

The ParseQueryString method uses UTF8 format to parse the query string In the returned NameValueCollection, URL-encoded characters are decoded and multiple occurrences of the same query string parameter are listed as a single entry with a comma separating each value.

Security noteSecurity Note:

The ParseQueryString method uses query strings that might contain user input, which is a potential security threat. By default, ASP.NET Web pages validate that user input does not include script or HTML elements. For more information, see Script Exploits Overview (Visual Studio).

The following code example demonstrates how to use the ParseQueryString method. Multiple occurrences of the same query string variable are consolidated in one entry of the returned NameValueCollection.

<%@ Page Language="C#"%>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
<script runat="server">

  protected void Page_Load(object sender, EventArgs e)
    String currurl = HttpContext.Current.Request.RawUrl;
    String querystring = null ;

    // Check to make sure some query string variables
    // exist and if not add some and redirect.
    int iqs = currurl.IndexOf('?');
    if (iqs == -1)
      String redirecturl = currurl + "?var1=1&var2=2+2%2f3&var1=3";
      Response.Redirect(redirecturl, true); 
    // If query string variables exist, put them in
    // a string.
    else if (iqs >= 0)
      querystring = (iqs < currurl.Length - 1) ? currurl.Substring(iqs + 1) : String.Empty;
    // Parse the query string variables into a NameValueCollection.
    NameValueCollection qscoll = HttpUtility.ParseQueryString(querystring);
    // Iterate through the collection.
    StringBuilder sb = new StringBuilder("<br />");
    foreach (String s in qscoll.AllKeys)
      sb.Append(s + " - " + qscoll[s] + "<br />");
    // Write the result to a label.
    ParseOutput.Text = sb.ToString();


<html xmlns="" >
<head runat="server">
    <title>HttpUtility ParseQueryString Example</title>
    <form id="form1" runat="server">
      Query string variables are:
      <asp:Label  id="ParseOutput"
                  runat="server" />

Windows 98, Windows Server 2000 SP4, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0

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