Select a specific range of elements?

I want to select a specific range of elements within my XML files

Here is an example of the XML:

<urlset>
    <url>
        <loc>e1</loc>
        <priority>1</priority>
    </url>
    <url>
        <loc>e2</loc>
        <priority>2</priority>
    </url>
    <url>
        开发者_运维问答<loc>e3</loc>
        <priority>1</priority>
    </url>
    <url>
        <loc>e4</loc>
        <priority>3</priority>
    </url>
    <url>
        <loc>e4</loc>
        <priority>1</priority>
    </url>
    <url>
        <loc>e5</loc>
        <priority>2</priority>
    </url>
</urlset>

How to get the value of e2 to e4?

---

var doc = XDocument.Parse(xml);

var result = doc.Element("urlset").Elements("url")
    .SkipWhile(x => x.Element("loc").Value != "e2")
    .TakeWhile(x => x.Element("loc").Value != "e4");

---

var result = urlset.Elements("url").Where(url =>
            url.Element("loc").Value.ToString().CompareTo("e2") >= 0 &&
            url.Element("loc").Value.ToString().CompareTo("e4") <= 0).Select(element => element.Element("loc").Value.ToString());

It uses standard (string) comparison - same as in alphabetical sorting, and it doesn't protect you against cases where some element would not have loc subelement at all (null reference exception would be thrown).

---

You can use this XPath:

//url[loc = 'e2' or 
    (preceding-sibling::url/loc = 'e2' and following-sibling::url/loc = 'e4')
]

It will select url with loc = e2, e3, e4

---

an alternative way:

var urls = from url in doc.Descendants("urlset").Elements("url")
    let str = Int32.Parse(url.Element("loc").Value.Replace("e",""))
    where str >= 2 && str <= 4  
    select url;

or actually, a safer option that doesn't throw exceptions if loc is not in the form "e + integer value" (courtesy of Marc Gravell) would be:

int? TryParse(string s)
{
    int i;
    return int.TryParse(s, out i) ? (int?)i : (int?)null;
}

var urls = from url in doc.Descendants("urlset").Elements("url")
    let str = TryParse(url.Element("loc").Value.Replace("e",""))
    where str >= 2 && str <= 4  
    select url;