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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)

'Declaration
Public Shared Function ParseQueryString ( _
	query As String _
) As NameValueCollection

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 Nothing.

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="VB" %>

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
    "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<script runat="server">

  Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs)

    Dim currurl As String = HttpContext.Current.Request.RawUrl
    Dim querystring As String = Nothing

    ' Check to make sure some query string variables
    ' exist and if not add some and redirect.
    Dim iqs As Int32 = currurl.IndexOf("?".ToCharArray())
    If (iqs = -1) Then

      Dim redirecturl As String = currurl & "?var1=1&var2=2+2%2f3&var1=3"
      Response.Redirect(redirecturl, True)

      ' If query string variables exist, put them in
      ' a string.
    ElseIf (iqs >= 0) Then

      If (iqs < currurl.Length - 1) Then
        querystring = currurl.Substring(iqs + 1)
      End If

    End If

    ' Parse the query string variables into a NameValueCollection.
    Dim qscoll As NameValueCollection = HttpUtility.ParseQueryString(querystring)

    ' Iterate through the collection.
    Dim sb As New StringBuilder("<br />")
    For Each s As String In qscoll.AllKeys

      sb.Append(s & " - " & qscoll(s) & "<br />")

    Next s

    ' Write the result to a label
    ParseOutput.Text = sb.ToString()

  End Sub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
<head id="Head1" 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: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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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