multiple sorting using AddSort method of the XPathExpression class

[milecimm]

Hi
I'm trying to sort a table that contains four columns. I've filled this table with data from an xml file. The idea is to sort the table by clicking on the header of the column. I'm not sure if this is the correct approach. I cannot use xsl and would like to maitain the same code structure but my AddSort method of the XPathExpression class doesnt semm to work. Thanks for your help.

My xml is

CONTRACTS
--CONTRACT
---SUPPLIER
---COMMODITIES
----COMMODITY
-----COMODDITYNAME




       Dim letter As String
        If Request.QueryString("letter") = "" Then
            letter = "A"
        ElseIf Request.QueryString("letter") = "All" Then
            letter = ""
        Else
            letter = Request.QueryString("letter")
        End If

        Dim SortingOrder As String = Nothing

        If Not Page.IsPostBack Then
            SortingOrder = XmlSortOrder.Ascending
            Session("getSortingOrder") = SortingOrder
        End If

        If Session("getSortingOrder") = XmlSortOrder.Ascending Then
            SortingOrder = XmlSortOrder.Descending
        End If

        Dim order As String = Nothing
        If Request.QueryString("sort") = "" Then
            order = "pf:NAME"
        ElseIf Request.QueryString("sort") = "name" Then
            order = "pf:NAME"
        ElseIf Request.QueryString("sort") = "commodity" Then
            order = "pf:COMMODITIES/pf:COMMODITY/pf:COMMODITYNAME"
        ElseIf Request.QueryString("sort") = "supplier" Then
            order = "pf:SUPPLIER"
        End If

        Dim myString As StringBuilder = New StringBuilder(10)
        Dim xdoc As New XPathDocument("local_xml.xml")
        Dim nav As XPathNavigator = xdoc.CreateNavigator()
        Dim expr As XPathExpression
        expr = nav.Compile("/pf:CONTRACTS/pf:CONTRACT[pf:NAME[starts-with(., '" & letter & "')]]")

        Dim namespaceManager As XmlNamespaceManager = New XmlNamespaceManager(nav.NameTable)
        namespaceManager.AddNamespace("pf", "http://namespace.ac.uk/")
        expr.AddSort(order, SortingOrder, XmlCaseOrder.None, String.Empty, XmlDataType.Text)
        expr.SetContext(namespaceManager)

        Dim nodes As XPathNodeIterator = nav.Select(expr)

        If nodes.Count > 0 Then

            Dim tr As String = Nothing
            myString.AppendLine("<table width='96%' border='0' cellpadding='0' cellspacing='0' border='0' class='datatable1'>")
            myString.AppendLine("<th width='35%'><a href='?letter=" & letter & "&sort=name'>Name</a></th><th width='35%'><a href='?letter=" & letter & "&sort=commodity'>Commodity</a></th><th width='20%'><a href='?letter=" & letter & "&sort=supplier'>Supplier</a></th>")

            While nodes.MoveNext()

                Dim node As XPathNavigator = nodes.Current.SelectSingleNode("pf:NAME", namespaceManager)
                 Dim supplier As XPathNavigator = nodes.Current.SelectSingleNode("pf:SUPPLIER", namespaceManager)
                Dim commodity As XPathNavigator = nodes.Current.SelectSingleNode("pf:COMMODITIES/pf:COMMODITY/pf:COMMODITYNAME", namespaceManager)
              
                Dim sChars As String = " "
                myString.AppendLine("<tr>")
                myString.AppendLine("<td>")
                myString.AppendLine(node.ToString())
                myString.AppendLine("</td>")
                myString.AppendLine("<td>")
                myString.AppendLine(commodity.ToString())
                myString.AppendLine("</td>")
                myString.AppendLine("<td>")
                myString.AppendLine(supplier.ToString())
                myString.AppendLine("</td>")
                myString.AppendLine("</tr>")

            End While

            myString.AppendLine("</table>")

            Dim strOutput As String = myString.ToString()
            lblOutput.Text = strOutput

        Else

            lblOutput.Text = "No results for your search<br/>"

        End If

[jkmyoung]

Ideally you should be able to call expr.AddSort multiple times, based on the sorting criteria, but I'm not sure how it works.
If this doesn't work, you could try changing your sort expression to combine both of the values.

But first off, how are you changing your querystring code to account for multiple sort criteria? Will you have a value stored in Request.QuerySt ring("sort2"), or something similar?

[milecimm]

Hi,
Thanks for your help. I've modified my code to take out the "multiple" sorting because my real problem is that my code doesn't sort at all. If I use "pf:SUPPLIE R" as my sorting criteria nothing happens, for example. I've done sorting before (see http://bytes.com/topic/xml/answers/8...h-unique-value) but when changing the xpath expression then the sorting doesn't work. Thanks again for your help.

contracts.aspx. vb

 Dim letter As String
        If Request.QueryString("letter") = "" Then
            letter = "A"
        ElseIf Request.QueryString("letter") = "All" Then
            letter = ""
        Else
            letter = Request.QueryString("letter")
        End If
        
        Dim myString As StringBuilder = New StringBuilder(200)
        Dim xdoc As New XPathDocument("local_xml.xml")
        
        Dim nav As XPathNavigator = xdoc.CreateNavigator()
        Dim expr As XPathExpression
        expr = nav.Compile("/pf:CONTRACTS/pf:CONTRACT[pf:NAME[starts-with(., '" & letter & "')]]")
       
        Dim namespaceManager As XmlNamespaceManager = New XmlNamespaceManager(nav.NameTable)
        namespaceManager.AddNamespace("pf", "http://namespace.ac.uk/")
        expr.AddSort("pf:SUPPLIER", XmlSortOrder.Ascending, XmlCaseOrder.None, String.Empty, XmlDataType.Text)
        expr.SetContext(namespaceManager)

        Dim nodes As XPathNodeIterator = nav.Select(expr)

        If nodes.Count > 0 Then

            myString.AppendLine("<table width='96%' border='0' cellpadding='0' cellspacing='0' border='0' class='datatable1'>")
            myString.AppendLine("<th width='35%'>Name</th><th width='35%'>Commodity</th><th width='20%'>Supplier</a></th>")

            While nodes.MoveNext()

                Dim node As XPathNavigator = nodes.Current.SelectSingleNode("pf:NAME", namespaceManager)
                Dim supplier As XPathNavigator = nodes.Current.SelectSingleNode("pf:SUPPLIER", namespaceManager)
                Dim commodity As XPathNavigator = nodes.Current.SelectSingleNode("pf:COMMODITIES/pf:COMMODITY/pf:COMMODITYNAME", namespaceManager)

                Dim sChars As String = " "
                myString.AppendLine("<tr>")
                myString.AppendLine("<td>")
                myString.AppendLine(node.ToString())
                myString.AppendLine("</td>")
                myString.AppendLine("<td>")
                myString.AppendLine(commodity.ToString())
                myString.AppendLine("</td>")
                myString.AppendLine("<td>")
                myString.AppendLine(supplier.ToString())
                myString.AppendLine("</td>")
                myString.AppendLine("</tr>")

            End While

            myString.AppendLine("</table>")

            Dim strOutput As String = myString.ToString()
            lblOutput.Text = strOutput

        Else

            lblOutput.Text = "No results for your search<br/>"

        End If

contracts.aspx

<asp:Label ID="lblOutput" runat="server"></asp:Label>
    
     <a href="contracts.aspx?letter=A">A</a> -
<a href="contracts.aspx?letter=B">B</a> -
<a href="contracts.aspx?letter=C">C</a> -
etc etc

My xml
CONTRACTS
-CONTRACT
--NAME
--SUPPLIER
--COMMODITIES
---COMMODITY
----COMMODITYNAME