Add XML Element after multiple elements

Question

I have this XML:

<Meals>
    <Meal>
        <Food course="starter">Soup</Food>
        <Food course="mains">Fish</Food>
        <Food course="dessert">Ice cream</Food>
    </Meal>
    <Meal>
        <Food course="starter">Soup</Food>
        <Food course="mains">Chicken</Food>
        <Food course="dessert">Cheese</Food>
    </Meal>
    <Meal>
        <Food course="starter">Melon</Food>
        <Food course="mains">lamb</Food>
        <Food course="dessert">Ice cream</Food>
    </Meal>
</Meals>

And this XPath expression:

//Food[@course='dessert' and text() = 'Ice cream']

This finds every dessert course of ice cream. I want to add a new element after each matching element like so:

<Meals>
    <Meal>
        <Food course="starter">Soup</Food>
        <Food course="mains">Fish</Food>
        <Food course="dessert">Ice cream</Food>
        <Review>enjoyed</Food>
    </Meal>
    <Meal>
        <Food course="starter">Soup</Food>
        <Food course="mains">Chicken</Food>
        <Food course="dessert">Cheese</Food>
    </Meal>
    <Meal>
        <Food course="starter">Melon</Food>
        <Food course="mains">lamb</Food>
        <Food course="dessert">Ice cream</Food>
        <Review>enjoyed</Food>
    </Meal>
</Meals>

How can I do this in C# given that XPath expression? The expression may alter (for example selecting mains instead), and the structure of the XML may vary too. Regardless a new element must be inserted after each matching element.

I know there is a AddAfterSelf method on an XElement, but I don't know how to use that on the collection of XElements the XPath expression may return.

Fabio · Accepted Answer · 2019-03-15 11:48:37Z

1

LINQ to XML

var doc = XDocument.Parse("filepath");

var enjoyedMeals = 
   doc.Descendants("Meal")
      .Where(meal => meal.Elements.Any(food => food.Attribute("course").Value == "desert"));

foreach (var meal in enjoyedMeals)
{
    var review = new XElement("Review", "enjoyed");
    meal.Elements.Add(review);
}

doc.ToString(); // contains <Review> elements

answered Mar 15, 2019 at 11:48

Fabio

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1 Comment

usefulcat Over a year ago

Thank you, this is very useful. However I have to use an XPath expression and the structure of the XML may alter so I can't reference any element properties in code. Regardless this has helped me find a solution, so it is much appreciated!

usefulcat · Accepted Answer · 2019-03-15 12:16:15Z

1

It's straightforward, but I needed a reminder from @Fabio that a foreach is what is necessary:

foreach (var element in foodXml.XPathSelectElements(xpathExpression))
{
    element.AddAfterSelf(new XElement($"Review", "enjoyed"));
}

foodXml now has the additional enjoyed element after the matching elements

answered Mar 15, 2019 at 12:16

usefulcat

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Comments

Alejandro · Accepted Answer · 2019-03-15 22:21:11Z

0

And this XPath expression:
//Food[@course='dessert' and text() = 'Ice cream']
This finds every Meal that has a dessert course of ice cream. I want to add a new element after each matching element like so:

That expression is wrong. You need:

/Meals/Meal[Food[@course = 'dessert'] = 'Ice cream']

answered Mar 15, 2019 at 22:21

Alejandro

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1 Comment

usefulcat Over a year ago

I've edited the question to make it clear the XPath finds 'every dessert course of ice cream' not 'every Meal that has a dessert course of ice cream'. The XPath is correct in the question. No problem with that, my question was how to add an element in C#. Thank you anyway

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