Filtering Data Using the XmlDataSource Control

Artykuł
10/22/2014

You can filter the XML data exposed by an XmlDataSource control by setting the control's XPath property to an XPath filtering expression. If you have specified an Extensible Stylesheet Language (XSL) style sheet to transform the data exposed by your XmlDataSource control, the XPath filtering expression is applied after the transformation takes place.

The following code example shows an XmlDataSource control bound to a TreeView control. The XML data is filtered using an XPath query.

<%@ 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">

Sub SelectRegion(sender AsObject, e As EventArgs)
  If RegionDropDownList.SelectedValue = "(Show All)"Then
    PeopleDataSource.XPath = "/People/Person"ElseDim selectedValue AsString = ""SelectCase RegionDropDownList.SelectedValue
      Case"CA"
        selectedValue = "CA"Case"HI"
        selectedValue = "HI"Case"WA"
        selectedValue = "WA"CaseElse        ' Invalid value.EndSelect

    PeopleDataSource.XPath = "/People/Person[Address/Region='" & selectedValue & "']"EndIf

  PeopleTreeView.DataBind()
EndSub

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
      <table border="0" cellpadding="3">
        <tr>
          <td valign="top">
            <b>Select Region:</b>
            <asp:DropDownList runat="server" id="RegionDropDownList" AutoPostBack="True"
                              OnSelectedIndexChanged="SelectRegion">                              
              <asp:ListItem Selected="True">(Show All)</asp:ListItem>
              <asp:ListItem>CA</asp:ListItem>
              <asp:ListItem>HI</asp:ListItem>
              <asp:ListItem>WA</asp:ListItem>
            </asp:DropDownList>
          </td>
          <td valign="top">
            <asp:XmlDataSource
              id="PeopleDataSource"
              runat="server"
              XPath="/People/Person"
              DataFile="~/App_Data/people.xml" />

            <asp:TreeView
              id="PeopleTreeView"
              runat="server"
              DataSourceID="PeopleDataSource">
              <DataBindings>
                <asp:TreeNodeBinding DataMember="LastName"    TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="FirstName"   TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Street"      TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="City"        TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Region"      TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="ZipCode"     TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Title"       TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Description" TextField="#InnerText" />
              </DataBindings>
            </asp:TreeView>
          </td>
        </tr>
      </table>
    </form>
  </body>
</html>

<%@ 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">

void SelectRegion(object sender, EventArgs e)
{
  if (RegionDropDownList.SelectedValue == "(Show All)")
    PeopleDataSource.XPath = "/People/Person";
  else
  {
    string selectedValue = "";

    switch (RegionDropDownList.SelectedValue)
    {
      case"CA":
        selectedValue = "CA";
        break;
      case"HI":
        selectedValue = "HI";
        break;
      case"WA":
        selectedValue = "WA";
        break;
      default:
        // Invalid value.break;
    }

    PeopleDataSource.XPath = "/People/Person[Address/Region='" + selectedValue + "']";
  }

  PeopleTreeView.DataBind();
}

</script>

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
      <table border="0" cellpadding="3">
        <tr>
          <td valign="top">
            <b>Select Region:</b>
            <asp:DropDownList runat="server" id="RegionDropDownList" AutoPostBack="True"
                              OnSelectedIndexChanged="SelectRegion">                              
              <asp:ListItem Selected="True">(Show All)</asp:ListItem>
              <asp:ListItem>CA</asp:ListItem>
              <asp:ListItem>HI</asp:ListItem>
              <asp:ListItem>WA</asp:ListItem>
            </asp:DropDownList>
          </td>
          <td valign="top">
            <asp:XmlDataSource
              id="PeopleDataSource"
              runat="server"
              XPath="/People/Person"
              DataFile="~/App_Data/people.xml" />

            <asp:TreeView
              id="PeopleTreeView"
              runat="server"
              DataSourceID="PeopleDataSource">
              <DataBindings>
                <asp:TreeNodeBinding DataMember="LastName"    TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="FirstName"   TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Street"      TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="City"        TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Region"      TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="ZipCode"     TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Title"       TextField="#InnerText" />
                <asp:TreeNodeBinding DataMember="Description" TextField="#InnerText" />
              </DataBindings>
            </asp:TreeView>
          </td>
        </tr>
      </table>
    </form>
  </body>
</html>

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Filtering Data Using the XmlDataSource Control

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