Extensions.Descendants 方法

定义

命名空间:
System.Xml.Linq
程序集:
System.Xml.XDocument.dll
程序集:
System.Xml.Linq.dll
程序集:
netstandard.dll

返回元素集合，其中包含源集合中每个元素和文档的子代元素。Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

重载

Descendants<T>(IEnumerable<T>, XName)

返回经过筛选的元素集合，其中包含源集合中每个元素和文档的子代元素。Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. 集合中仅包括具有匹配 XName 的元素。Only elements that have a matching XName are included in the collection.
Descendants<T>(IEnumerable<T>)

返回元素集合，其中包含源集合中每个元素和文档的子代元素。Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

注解

Visual Basic 用户可以使用集成的 XML 子代轴检索集合的子代元素。Visual Basic users can use the integrated XML descendant axis to retrieve the descendant elements of a collection. 但是，集成的轴仅检索具有指定名称的后代。However, the integrated axis only retrieves descendants with a specified name. 如果 Visual Basic 用户要检索所有后代，则必须显式使用此轴方法。If Visual Basic users want to retrieve all descendants, then they must use this axis method explicitly.

此方法使用延迟执行。This method uses deferred execution.

Descendants<T>(IEnumerable<T>, XName)

返回经过筛选的元素集合，其中包含源集合中每个元素和文档的子代元素。Returns a filtered collection of elements that contains the descendant elements of every element and document in the source collection. 集合中仅包括具有匹配 XName 的元素。Only elements that have a matching XName are included in the collection.

public:
generic <typename T>
 where T : System::Xml::Linq::XContainer[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Xml::Linq::XElement ^> ^ Descendants(System::Collections::Generic::IEnumerable<T> ^ source, System::Xml::Linq::XName ^ name);
public static System.Collections.Generic.IEnumerable<System.Xml.Linq.XElement> Descendants<T> (this System.Collections.Generic.IEnumerable<T> source, System.Xml.Linq.XName name) where T : System.Xml.Linq.XContainer;
public static System.Collections.Generic.IEnumerable<System.Xml.Linq.XElement> Descendants<T> (this System.Collections.Generic.IEnumerable<T>? source, System.Xml.Linq.XName? name) where T : System.Xml.Linq.XContainer;
static member Descendants : seq<'T (requires 'T :> System.Xml.Linq.XContainer)> * System.Xml.Linq.XName -> seq<System.Xml.Linq.XElement> (requires 'T :> System.Xml.Linq.XContainer)
<Extension()>
Public Function Descendants(Of T As XContainer) (source As IEnumerable(Of T), name As XName) As IEnumerable(Of XElement)

类型参数

T

source 中对象的类型，被约束为 XContainer。The type of the objects in source, constrained to XContainer.

参数

source
IEnumerable<T>

一个包含源集合的 IEnumerable<T> 的 XContainer。An IEnumerable<T> of XContainer that contains the source collection.

name
XName

要匹配的 XName。The XName to match.

返回

IEnumerable<XElement>

IEnumerable<T> 的 XElement，其中包含源集合中每个元素和文档的子代元素。An IEnumerable<T> of XElement that contains the descendant elements of every element and document in the source collection. 集合中仅包括具有匹配 XName 的元素。Only elements that have a matching XName are included in the collection.

示例

下面的示例检索两个元素的集合，然后检索具有指定元素名称的两个元素的所有后代的集合。The following example retrieves a collection of two elements, and then retrieves a collection of all descendants of the two elements that have the specified element name.

XElement xmlTree = XElement.Parse(  
@"<Root>  
    <Para>  
        <t>This is some text </t>  
        <b>  
            <t>where</t>  
        </b>  
        <t> all of the text nodes must be concatenated. </t>  
    </Para>  
    <Para>  
        <t>This is a second sentence.</t>  
    </Para>  
</Root>");  

string str =  
    (from el in xmlTree.Elements("Para").Descendants("t")  
    select (string)el)  
    .Aggregate(new StringBuilder(),  
        (sb, i) => sb.Append(i),  
        sb => sb.ToString());  

Console.WriteLine(str);  

Dim xmlTree As XElement = _  
    <Root>  
        <Para>  
            <t>This is some text </t>  
            <b>  
                <t>where</t>  
            </b>  
            <t> all of the text nodes must be concatenated. </t>  
        </Para>  
        <Para>  
            <t>This is a second sentence.</t>  
        </Para>  
    </Root>  

Dim str As String = _  
    ( _  
        From el In xmlTree.<Para>...<t> _  
        Select CStr(el) _  
    ) _  
    .Aggregate(New StringBuilder(), _  
               Function(ByVal sb, ByVal i) sb.Append(i), _  
               Function(ByVal sb) sb.ToString())  

Console.WriteLine(str)

该示例产生下面的输出：This example produces the following output:

This is some text where all of the text nodes must be concatenated. This is a second sentence.

下面是同一个示例，但在这种情况下，XML 位于命名空间中。The following is the same example, but in this case the XML is in a namespace. 有关详细信息，请参阅 使用 XML 命名空间。For more information, see Work with XML Namespaces.

XNamespace aw = "http://www.adventure-works.com";  
XElement xmlTree = XElement.Parse(  
@"<Root xmlns='http://www.adventure-works.com'>  
    <Para>  
        <t>This is some text </t>  
        <b>  
            <t>where</t>  
        </b>  
        <t> all of the text nodes must be concatenated. </t>  
    </Para>  
    <Para>  
        <t>This is a second sentence.</t>  
    </Para>  
</Root>");  

string str =  
    (from el in xmlTree.Elements(aw + "Para").Descendants(aw + "t")  
     select (string)el)  
    .Aggregate(new StringBuilder(),  
        (sb, i) => sb.Append(i),  
        sb => sb.ToString());  

Console.WriteLine(str);  

Imports <xmlns="http://www.adventure-works.com">  

Module Module1  
    Sub Main()  
        Dim xmlTree As XElement = _  
            <Root>  
                <Para>  
                    <t>This is some text </t>  
                    <b>  
                        <t>where</t>  
                    </b>  
                    <t> all of the text nodes must be concatenated. </t>  
                </Para>  
                <Para>  
                    <t>This is a second sentence.</t>  
                </Para>  
            </Root>  

        Dim str As String = _  
            ( _  
                From el In xmlTree.<Para>...<t> _  
                Select CStr(el) _  
            ) _  
            .Aggregate(New StringBuilder(), _  
                       Function(sb, i) sb.Append(i), _  
                       Function(sb) sb.ToString())  

        Console.WriteLine(str)  
    End Sub  
End Module

该示例产生下面的输出：This example produces the following output:

This is some text where all of the text nodes must be concatenated. This is a second sentence.

注解

Visual Basic 用户可以使用 Visual Basic () LINQ to XML 中的语言集成轴 ，而不是显式使用此轴方法。Visual Basic users can use the Language-Integrated Axes in Visual Basic (LINQ to XML) instead of using this axis method explicitly.

此方法使用延迟执行。This method uses deferred execution.

另请参阅

适用于

Descendants<T>(IEnumerable<T>)

返回元素集合，其中包含源集合中每个元素和文档的子代元素。Returns a collection of elements that contains the descendant elements of every element and document in the source collection.

public:
generic <typename T>
 where T : System::Xml::Linq::XContainer[System::Runtime::CompilerServices::Extension]
 static System::Collections::Generic::IEnumerable<System::Xml::Linq::XElement ^> ^ Descendants(System::Collections::Generic::IEnumerable<T> ^ source);
public static System.Collections.Generic.IEnumerable<System.Xml.Linq.XElement> Descendants<T> (this System.Collections.Generic.IEnumerable<T> source) where T : System.Xml.Linq.XContainer;
public static System.Collections.Generic.IEnumerable<System.Xml.Linq.XElement> Descendants<T> (this System.Collections.Generic.IEnumerable<T>? source) where T : System.Xml.Linq.XContainer;
static member Descendants : seq<'T (requires 'T :> System.Xml.Linq.XContainer)> -> seq<System.Xml.Linq.XElement> (requires 'T :> System.Xml.Linq.XContainer)
<Extension()>
Public Function Descendants(Of T As XContainer) (source As IEnumerable(Of T)) As IEnumerable(Of XElement)

类型参数

T

source 中对象的类型，被约束为 XContainer。The type of the objects in source, constrained to XContainer.

参数

source
IEnumerable<T>

一个包含源集合的 IEnumerable<T> 的 XContainer。An IEnumerable<T> of XContainer that contains the source collection.

返回

IEnumerable<XElement>

IEnumerable<T> 的 XElement，其中包含源集合中每个元素和文档的子代元素。An IEnumerable<T> of XElement that contains the descendant elements of every element and document in the source collection.

示例

下面的示例检索元素的集合，然后使用此轴方法检索元素集合中每个项的所有子代元素。The following example retrieves a collection of elements, and then uses this axis method to retrieve all descendent elements of every item in the collection of elements.

XElement xmlTree = XElement.Parse(  
@"<Root>  
    <Para>  
        <t>This is some text </t>  
        <b>  
            <t>where</t>  
        </b>  
        <t> all of the nodes must be concatenated. </t>  
    </Para>  
    <Para>  
        <t>This is a second sentence.</t>  
    </Para>  
</Root>");  

IEnumerable<XElement> elList =  
    from el in xmlTree.Elements("Para").Descendants()  
    select el;  

foreach (XElement el in elList)  
    Console.WriteLine(el);  

Dim xmlTree As XElement = _  
    <Root>  
        <Para>  
            <t>This is some text </t>  
            <b>  
                <t>where</t>  
            </b>  
            <t> all of the nodes must be concatenated. </t>  
        </Para>  

        <Para>  
            <t>This is a second sentence.</t>  
        </Para>  
    </Root>  

Dim elList = From el In xmlTree.<Para>.Descendants _  
                        Select el  

For Each el As XElement In elList  
    Console.WriteLine(el)  
Next

该示例产生下面的输出：This example produces the following output:

<t>This is some text </t>  
<b>  
  <t>where</t>  
</b>  
<t>where</t>  
<t> all of the nodes must be concatenated. </t>  
<t>This is a second sentence.</t>

下面是同一个示例，但在这种情况下，XML 位于命名空间中。The following is the same example, but in this case the XML is in a namespace. 有关详细信息，请参阅 使用 XML 命名空间。For more information, see Work with XML Namespaces.

XNamespace aw = "http://www.adventure-works.com";  
XElement xmlTree = XElement.Parse(  
@"<Root xmlns='http://www.adventure-works.com'>  
    <Para>  
        <t>This is some text </t>  
        <b>  
            <t>where</t>  
        </b>  
        <t> all of the nodes must be concatenated. </t>  
    </Para>  
    <Para>  
        <t>This is a second sentence.</t>  
    </Para>  
</Root>");  

IEnumerable<XElement> elList =  
    from el in xmlTree.Elements(aw + "Para").Descendants()  
    select el;  

foreach (XElement el in elList)  
    Console.WriteLine(el);  

Imports <xmlns="http://www.adventure-works.com">  

Module Module1  
    Sub Main()  
        Dim xmlTree As XElement = _  
            <Root>  
                <Para>  
                    <t>This is some text </t>  
                    <b>  
                        <t>where</t>  
                    </b>  
                    <t> all of the nodes must be concatenated. </t>  
                </Para>  

                <Para>  
                    <t>This is a second sentence.</t>  
                </Para>  
            </Root>  

        Dim elList = From el In xmlTree.<Para>.Descendants _  
                                Select el  

        For Each el As XElement In elList  
            Console.WriteLine(el)  
        Next  
    End Sub  
End Module

该示例产生下面的输出：This example produces the following output:

<t xmlns="http://www.adventure-works.com">This is some text </t>  
<b xmlns="http://www.adventure-works.com">  
  <t>where</t>  
</b>  
<t xmlns="http://www.adventure-works.com">where</t>  
<t xmlns="http://www.adventure-works.com"> all of the nodes must be concatenated. </t>  
<t xmlns="http://www.adventure-works.com">This is a second sentence.</t>

注解

Visual Basic 用户可以使用集成的 XML 子代轴检索集合的子代元素。Visual Basic users can use the integrated XML descendant axis to retrieve the descendant elements of a collection. 但是，集成的轴仅检索具有指定名称的后代。However, the integrated axis only retrieves descendants with a specified name. 如果 Visual Basic 用户要检索所有后代，则必须显式使用此轴方法。If Visual Basic users want to retrieve all descendants, then they must use this axis method explicitly.

此方法使用延迟执行。This method uses deferred execution.

另请参阅

适用于