How can I move an XML element above the previous element using LINQ to XML?

Question

I have the following XML structure:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<Root xmlns:xsi="My Program">
    <NotRoot Text="Hello">
        <SomeOption Text="Option 1" Centered="False">
            <SomeOption Text="Option 1.1" Centered="False">
                <SomeOption Text="Option 1.1.1" Centered="false">
                    <SomeOption Text="A" Centered="false">
                        <SpecialName Text="Blah blah" Centered="false">
                            <Number>1</Number>
                        </SpecialName>
                    </SomeOption>
                    <SomeOption Text="B" Centered="false">
                        <SpecialName Text="Hi" Centered="true">
                            <SomeStrangeName>42</SomeStrangeName>
                        </SpecialName>
                    </SomeOption>
                    <SomeOption Text="C" Centered="false">
                        <SpecialName Text="Some text here" Centered="false">
                            <Stuff>
                                <Thing1>10</Thing1>
                                <Thing2>20</Thing2>
                                <Thing3>30</Thing3>
                            </Stuff>
                        </SpecialName>
                    </SomeOption>
                    <SomeOption Text="D" Centered="false">
                        <SpecialName Text="Bye" Centered="false">
                            <Things>
                                <Random1>9846516981</Random1>
                                <Random2>8784749874</Random2>
                            </Things>
                        </SpecialName>
                    </SomeOption>
                </SomeOption>
            </SomeOption>
        </SomeOption>
    </NotRoot>
</Root>

I would like to move the element "C" up one position so that the output looks like this:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<Root xmlns:xsi="My Program">
    <NotRoot Text="Hello">
        <SomeOption Text="Option 1" Centered="False">
            <SomeOption Text="Option 1.1" Centered="False">
                <SomeOption Text="Option 1.1.1" Centered="false">
                    <SomeOption Text="A" Centered="false">
                        <SpecialName Text="Blah blah" Centered="false">
                            <Number>1</Number>
                        </SpecialName>
                    </SomeOption>
                    <SomeOption Text="C" Centered="false">
                        <SpecialName Text="Some text here" Centered="false">
                            <Stuff>
                                <Thing1>10</Thing1>
                                <Thing2>20</Thing2>
                                <Thing3>30</Thing3>
                            </Stuff>
                        </SpecialName>
                    </SomeOption>
                    <SomeOption Text="B" Centered="false">
                        <SpecialName Text="Hi" Centered="true">
                            <SomeStrangeName>42</SomeStrangeName>
                        </SpecialName>
                    </SomeOption>
                    <SomeOption Text="D" Centered="false">
                        <SpecialName Text="Bye" Centered="false">
                            <Things>
                                <Random1>9846516981</Random1>
                                <Random2>8784749874</Random2>
                            </Things>
                        </SpecialName>
                    </SomeOption>
                </SomeOption>
            </SomeOption>
        </SomeOption>
    </NotRoot>
</Root>

My "Move Element Up" button can recognize the element to move and the element above it with this code:

public void MoveElementUp(XElement xeElementToMove)
{
    XElement xeElementToMoveInXML = xmlRoot.Descendants().Single(xe => xe == xeElementToMove);
    XElement xePrevious = XElement.Parse(xeElementToMoveInXML.PreviousNode.ToString());

    // Do something here to put xeElementToMoveInXML before xePrevious

    SaveXML();
}

I think I may be going about it the wrong way though. Perhaps I need to parse it all as regular text, then move it somehow, then convert it back to XML elements?

Answer 1

Simple:

• Find its current "previous" element
• Remove it from the tree
• Insert it before the element you found

Something like this:

static void MoveElementUp(XElement element)
{
    // Walk backwards until we find an element - ignore text nodes
    XNode previousNode = element.PreviousNode;
    while (previousNode != null && !(previousNode is XElement))
    {
        previousNode = previousNode.PreviousNode;
    }
    if (previousNode == null)
    {
        throw new ArgumentException("Nowhere to move element to!");
    }
    element.Remove();
    previousNode.AddBeforeSelf(element);
}