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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
)

Parameters

query
Type: System.String
The query string to parse.

Return Value

Type: System.Collections.Specialized.NameValueCollection
A NameValueCollection of query parameters and values.

ExceptionCondition
ArgumentNullException

query is null.

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.

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"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<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();

  }
</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head runat="server">
    <title>HttpUtility ParseQueryString Example</title>
</head>
<body>
    <form id="form1" runat="server">
      Query string variables are:
      <asp:Label  id="ParseOutput"
                  runat="server" />
    </form>
</body>
</html>


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

The .NET Framework does not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

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