What is the difference between Linq to XML Descendants and Elements

Question

I have came across both these keywords in the VS IntelliSense. I tried to googling the difference between them and did not get a clear answer. Which one of these have the best performance with small to medium XML files. Thanks

Answer 1

Elements finds only those elements that are direct descendents, ie immediate children.

Descendants finds children at any level, ie children, grand-children, etc...

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Here is an example demonstrating the difference:

<?xml version="1.0" encoding="utf-8" ?>
<foo>
    <bar>Test 1</bar>
    <baz>
        <bar>Test 2</bar>
    </baz>
    <bar>Test 3</bar>
</foo>

Code:

XDocument doc = XDocument.Load("input.xml");
XElement root = doc.Root;

foreach (XElement e in root.Elements("bar"))
{
    Console.WriteLine("Elements : " + e.Value);
}

foreach (XElement e in root.Descendants("bar"))
{
    Console.WriteLine("Descendants : " + e.Value);
}

Result:

Elements : Test 1
Elements : Test 3
Descendants : Test 1
Descendants : Test 2
Descendants : Test 3

If you know that the elements you want are immediate children then you will get better performance if you use Elements instead of Descendants .

Answer 2

Descendants将搜索当前元素的整个子树以获取指定的名称（如果未提供名称，则将返回树的扁平版本），而Elements仅搜索当前元素的直接子元素。