Article
11/18/2011

XContainer.AddFirst Method (array<Object[])

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Adds the specified content as the first children of this document or element.

Namespace: System.Xml.Linq
Assembly: System.Xml.Linq (in System.Xml.Linq.dll)

Syntax

'Declaration
Public Sub AddFirst ( _
    ParamArray content As Object() _
)

public void AddFirst(
    params Object[] content
)

Parameters

content
Type: array<System.Object[]
A parameter list of content objects.

Exceptions

Exception	Condition
InvalidOperationException	The parent is nulla null reference (Nothing in Visual Basic).

Remarks

This method adds the new content before the existing content of the XContainer.

For details about the valid content that can be passed to this function, see Valid Content of XElement and XDocument Objects.

This method will raise the Changed and the Changing events.

Examples

The following example creates two XML trees, and uses this method to add an XElement object as the first element to one of them. It also adds the results of a LINQ query to the XML tree.

Dim output As New StringBuilder
Dim srcTree As XElement = _
        <Root>
            <Element1>1</Element1>
            <Element2>2</Element2>
            <Element3>3</Element3>
            <Element4>4</Element4>
            <Element5>5</Element5>
        </Root>

Dim xmlTree As XElement = _
        <Root>
            <Child1>1</Child1>
            <Child2>2</Child2>
            <Child3>3</Child3>
            <Child4>4</Child4>
            <Child5>5</Child5>
        </Root>

xmlTree.AddFirst(New XElement("NewChild", "new content"))
xmlTree.AddFirst( _
    From el In srcTree.Elements() _
    Where CInt(el) > 3 _
    Select el _
)
' Even though Child9 does not exist in srcTree, the following statement will not
' throw an exception, and nothing will be added to xmlTree.
xmlTree.AddFirst(srcTree.<Child9>)
output.Append(xmlTree)
output.Append(Environment.NewLine)

OutputTextBlock.Text = output.ToString()

StringBuilder output = new StringBuilder();
XElement srcTree = new XElement("Root",
    new XElement("Element1", 1),
    new XElement("Element2", 2),
    new XElement("Element3", 3),
    new XElement("Element4", 4),
    new XElement("Element5", 5)
);
XElement xmlTree = new XElement("Root",
    new XElement("Child1", 1),
    new XElement("Child2", 2),
    new XElement("Child3", 3),
    new XElement("Child4", 4),
    new XElement("Child5", 5)
);
xmlTree.AddFirst(new XElement("NewChild", "new content"));
xmlTree.AddFirst(
    from el in srcTree.Elements()
    where (int)el > 3
    select el
);
// Even though Child9 does not exist in srcTree, the following statement will not
// throw an exception, and nothing will be added to xmlTree.
xmlTree.AddFirst(srcTree.Element("Child9"));
output.Append(xmlTree  + Environment.NewLine);

OutputTextBlock.Text = output.ToString();

Version Information

Silverlight

Supported in: 5, 4, 3

Silverlight for Windows Phone

Supported in: Windows Phone OS 7.1, Windows Phone OS 7.0

XNA Framework

Supported in: Xbox 360, Windows Phone OS 7.0

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.

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