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Фильтрация данных с помощью элемента управления XmlDataSource

  • Статья

Обновлен: Ноябрь 2007

Можно отфильтровать данные XML, представленные элементом управления XmlDataSource при установке свойства XPath равным фильтрующему выражению XPath. Если указана необходимость преобразования страницы данных стиля XSL, представленных элементом управления XmlDataSource, то фильтрующее выражение XPath применяется после трансформации.

В следующем примере кода показан элемент управления XmlDataSource, связанный с элементом управления TreeView. XML-данные фильтруются с помощью запроса XPath.

<%@ 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 As Object, e As EventArgs)
  If RegionDropDownList.SelectedValue = "(Show All)" Then
    PeopleDataSource.XPath = "/People/Person"
  Else
    Dim selectedValue As String = ""

    Select Case RegionDropDownList.SelectedValue
      Case "CA"
        selectedValue = "CA"
      Case "HI"
        selectedValue = "HI"
      Case "WA"
        selectedValue = "WA"
      Case Else
        ' Invalid value.
    End Select

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

  PeopleTreeView.DataBind()
End Sub

</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>

См. также

Основные понятия

Общие сведения о серверном веб-элементе управления XmlDataSource