XPathBinder.Eval Method

Reference

Definition

Namespace:: System.Web.UI

Assembly:: System.Web.dll

Important

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Parses and evaluates an XPath data-binding expression against an IXPathNavigable object at run time.

Overloads

Eval(Object, String)	Evaluates XPath data-binding expressions at run time.
Eval(Object, String, String)	Evaluates XPath data-binding expressions at run time and formats the result as text to be displayed in the requesting browser.
Eval(Object, String, IXmlNamespaceResolver)	Evaluates XPath data-binding expressions at run time and formats the result as text to be displayed in the requesting browser, using the IXmlNamespaceResolver object specified to resolve namespace prefixes in the XPath expression.
Eval(Object, String, String, IXmlNamespaceResolver)	Evaluates XPath data-binding expressions at run time and formats the result as text to be displayed in the requesting browser, using the IXmlNamespaceResolver object specified to resolve namespace prefixes in the XPath expression.

Eval(Object, String)

Evaluates XPath data-binding expressions at run time.

public:
 static System::Object ^ Eval(System::Object ^ container, System::String ^ xPath);

public static object Eval (object container, string xPath);

static member Eval : obj * string -> obj

Public Shared Function Eval (container As Object, xPath As String) As Object

Parameters

container: Object

The IXPathNavigable object reference that the expression is evaluated against. This must be a valid object identifier in the page's specified language.

xPath: String

The XPath query from container to the property value that is placed in the bound control property.

Returns

Object

An Object that results from the evaluation of the data-binding expression.

Exceptions

ArgumentNullException

The container or xpath parameter is null.

ArgumentException

The object specified by container is not an IXPathNavigable object.

Examples

The following code example demonstrates how to use an XmlDataSource control with a templated Repeater control to display XML data. This example has two parts:

A Web Forms page that displays XML data.
An XML file that contains the data.

The first part of the example shows a Web Forms page that displays XML data accessed through an XmlDataSource control. A Repeater control uses the simplified Eval(Object, String) method syntax to bind to data items within the XML document that the XmlDataSource represents. It uses the Select(Object, String) method to retrieve an IEnumerable list and assign it as a late-bound DataSource property for the Repeater control.

<%@ Page Language="C#" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
      <asp:XmlDataSource
        runat="server"
        id="XmlDataSource1"
        DataFile="bookstore2.xml"
        XPath="bookstore/genre[@name='fiction']" />

      <asp:Repeater
        runat="server"
        DataSourceID="XmlDataSource1">
        <ItemTemplate>
            <h1><%# XPath ("book/title") %></h1>
            <b>Author:</b>
            <%# XPath ("book/author/firstname") %>
            <%# XPath ("book/author/lastname") %>
            <asp:Repeater
                 DataSource='<%# XPathSelect ("book/chapters") %>'
                 runat="server">
                <ItemTemplate>
                     <%# XPath ("chapter/@name") %>
                </ItemTemplate>
            </asp:Repeater>
        </ItemTemplate>
    </asp:Repeater>
  </form>
  </body>
</html>

<%@ Page Language="VB" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<html xmlns="http://www.w3.org/1999/xhtml" >
  <head runat="server">
    <title>ASP.NET Example</title>
</head>
<body>
    <form id="form1" runat="server">
      <asp:XmlDataSource
        runat="server"
        id="XmlDataSource1"
        DataFile="bookstore2.xml"
        XPath="bookstore/genre[@name='fiction']" />

      <asp:Repeater
        runat="server"
        DataSourceID="XmlDataSource1">
        <ItemTemplate>
            <h1><%# XPath ("book/title") %></h1>
            <b>Author:</b>
            <%# XPath ("book/author/firstname") %>
            <%# XPath ("book/author/lastname") %>
            <asp:Repeater
                 DataSource='<%# XPathSelect ("book/chapters") %>'
                 runat="server">
                <ItemTemplate>
                     <%# XPath ("chapter/@name") %>
                </ItemTemplate>
            </asp:Repeater>
        </ItemTemplate>
    </asp:Repeater>
  </form>
  </body>
</html>

The second example provides the XML file, Bookstore2.xml, that is used as the source of the data displayed in the Web Forms page defined above.

<?xml version="1.0" encoding="iso-8859-1"?>  
  <bookstore>  
    <genre name="fiction">  
      <book ISBN="10-861003-324">  
        <author>  
          <firstname>test</firstname>  
          <lastname>test2</lastname>  
        </author>  
        <title>The Handmaid's Tale</title>  
        <price>12.95</price>  
        <chapters>  
          <chapter num="1" name="Introduction" />   
          <chapter num="2" name="Body" />   
          <chapter num="3" name="Conclusion" />  
        </chapters>  
      </book>  
    </genre>  
    <genre name="nonfiction">  
      <book genre="nonfiction" ISBN="1-861001-57-5">  
        <author>  
          <firstname>test3</firstname>  
          <lastname>test4</lastname>  
        </author>      
        <title>Pride And Prejudice</title>  
        <price>24.95</price>  
        <chapters>  
          <chapter num="1" name="Introduction" />   
          <chapter num="2" name="Body" />  
          <chapter num="3" name="Conclusion" />  
        </chapters>  
      </book>  
    </genre>  
  </bookstore>

Remarks

You can use the Eval method declaratively if you want to simplify the casting of an XML node to a text string to be displayed on a browser. To do so, you must place the <%# and %> tags, which are also used in standard ASP.NET data binding, around the data-binding expression.

For any of the list ASP.NET server controls, such as DataList, DataGrid, or Repeater, the container parameter should be Container.DataItem. If you are binding against the page, the container parameter should be Page.

Applies to

Eval(Object, String, String)

Evaluates XPath data-binding expressions at run time and formats the result as text to be displayed in the requesting browser.

public:
 static System::String ^ Eval(System::Object ^ container, System::String ^ xPath, System::String ^ format);

public static string Eval (object container, string xPath, string format);

static member Eval : obj * string * string -> string

Public Shared Function Eval (container As Object, xPath As String, format As String) As String

Parameters

container: Object

The IXPathNavigable object reference that the expression is evaluated against. This must be a valid object identifier in the page's specified language.

xPath: String

The XPath query from the container to the property value to be placed in the bound control property.

format: String

A .NET Framework format string, similar to those used by Format(String, Object), that converts the IXPathNavigable object (which results from the evaluation of the data-binding expression) to a String that can be displayed by the requesting browser.

Returns

String

A String that results from the evaluation of the data-binding expression and conversion to a string type.

Exceptions

ArgumentNullException

The container or xpath parameter is null.

ArgumentException

The object specified by container is not an IXPathNavigable.

Remarks

To learn more about format strings in the .NET Framework, see Formatting Types.

You can use the Eval(Object, String) method declaratively if you want to simplify the casting of an XML node to a text string to be displayed in a browser. To do so, you must place the <%# and %> tags, which are also used in standard ASP.NET data binding, around the data-binding expression.

Applies to

Eval(Object, String, IXmlNamespaceResolver)

Evaluates XPath data-binding expressions at run time and formats the result as text to be displayed in the requesting browser, using the IXmlNamespaceResolver object specified to resolve namespace prefixes in the XPath expression.

public:
 static System::Object ^ Eval(System::Object ^ container, System::String ^ xPath, System::Xml::IXmlNamespaceResolver ^ resolver);

public static object Eval (object container, string xPath, System.Xml.IXmlNamespaceResolver resolver);

static member Eval : obj * string * System.Xml.IXmlNamespaceResolver -> obj

Public Shared Function Eval (container As Object, xPath As String, resolver As IXmlNamespaceResolver) As Object

Parameters

container: Object

The IXPathNavigable object reference that the expression is evaluated against. This must be a valid object identifier in the page's specified language.

xPath: String

The XPath query from the container to the property value to be placed in the bound control property.

resolver: IXmlNamespaceResolver

The IXmlNamespaceResolver object used to resolve namespace prefixes in the XPath expression.

Returns

Object

A Object that results from the evaluation of the data-binding expression.

Remarks

You can use the Eval method declaratively if you want to simplify the casting of an XML node to a text string to be displayed in a browser. To do so, you must place the <%# and %> tags, which are also used in standard ASP.NET data binding, around the data-binding expression. The data-binding expression includes the XPath expression and an IXmlNamespaceResolver object to resolve the namespace reference.

Applies to

Eval(Object, String, String, IXmlNamespaceResolver)

public:
 static System::String ^ Eval(System::Object ^ container, System::String ^ xPath, System::String ^ format, System::Xml::IXmlNamespaceResolver ^ resolver);

public static string Eval (object container, string xPath, string format, System.Xml.IXmlNamespaceResolver resolver);

static member Eval : obj * string * string * System.Xml.IXmlNamespaceResolver -> string

Public Shared Function Eval (container As Object, xPath As String, format As String, resolver As IXmlNamespaceResolver) As String

Parameters

container: Object

The IXPathNavigable object reference that the expression is evaluated against. This must be a valid object identifier in the page's specified language.

xPath: String

The XPath query from the container to the property value to be placed in the bound control property.

format: String

resolver: IXmlNamespaceResolver

The IXmlNamespaceResolver object used to resolve namespace prefixes in the XPath expression.

Returns

String

A String that results from the evaluation of the data-binding expression and conversion to a string type.

Remarks

Applies to

Compartir a través de

XPathBinder.Eval Method

Definition

Overloads

Eval(Object, String)

Parameters

Returns

Exceptions

Examples

Remarks

See also

Applies to

Eval(Object, String, String)

Parameters

Returns

Exceptions

Remarks

See also

Applies to

Eval(Object, String, IXmlNamespaceResolver)

Parameters

Returns

Remarks

Applies to

Eval(Object, String, String, IXmlNamespaceResolver)

Parameters

Returns

Remarks

Applies to

Recursos adicionales