Best way to get InnerXml of an XElement?

What's the best way to get the contents of the mixed body element in the code below? The element might contain either XHTML or text, but I just want its contents in string form. The XmlElement type has the InnerXml property which is exactly what I'm after.

The code as written almost does what I want, but includes the surrounding <body>...</body> element, which I don't want.

XDocument doc = XDocument.Load(new StreamReader(s));
var templates = from t in doc.Descendants("template")
                where t.Attribute("name").Value == templateName
                select new
                {
                   Subject = t.Element("subject").Value,
                   Body = t.Element("body").ToString()
                };

标签： .net xml xelement innerxml

15条回答

听够珍惜

2楼-- · 2019-01-02 17:46

I wanted to see which of these suggested solutions performed best, so I ran some comparative tests. Out of interest, I also compared the LINQ methods to the plain old System.Xml method suggested by Greg. The variation was interesting and not what I expected, with the slowest methods being more than 3 times slower than the fastest.

The results ordered by fastest to slowest:

CreateReader - Instance Hunter (0.113 seconds)
Plain old System.Xml - Greg Hurlman (0.134 seconds)
Aggregate with string concatenation - Mike Powell (0.324 seconds)
StringBuilder - Vin (0.333 seconds)
String.Join on array - Terry (0.360 seconds)
String.Concat on array - Marcin Kosieradzki (0.364)

Method

I used a single XML document with 20 identical nodes (called 'hint'):

<hint>
  <strong>Thinking of using a fake address?</strong>
  <br />
  Please don't. If we can't verify your address we might just
  have to reject your application.
</hint>

The numbers shown as seconds above are the result of extracting the "inner XML" of the 20 nodes, 1000 times in a row, and taking the average (mean) of 5 runs. I didn't include the time it took to load and parse the XML into an XmlDocument (for the System.Xml method) or XDocument (for all the others).

The LINQ algorithms I used were: (C# - all take an XElement "parent" and return the inner XML string)

CreateReader:

var reader = parent.CreateReader();
reader.MoveToContent();

return reader.ReadInnerXml();

Aggregate with string concatenation:

return parent.Nodes().Aggregate("", (b, node) => b += node.ToString());

StringBuilder:

StringBuilder sb = new StringBuilder();

foreach(var node in parent.Nodes()) {
    sb.Append(node.ToString());
}

return sb.ToString();

String.Join on array:

return String.Join("", parent.Nodes().Select(x => x.ToString()).ToArray());

String.Concat on array:

return String.Concat(parent.Nodes().Select(x => x.ToString()).ToArray());

I haven't shown the "Plain old System.Xml" algorithm here as it's just calling .InnerXml on nodes.

Conclusion

If performance is important (e.g. lots of XML, parsed frequently), I'd use Daniel's CreateReader method every time. If you're just doing a few queries, you might want to use Mike's more concise Aggregate method.

If you're using XML on large elements with lots of nodes (maybe 100's), you'd probably start to see the benefit of using StringBuilder over the Aggregate method, but not over CreateReader. I don't think the Join and Concat methods would ever be more efficient in these conditions because of the penalty of converting a large list to a large array (even obvious here with smaller lists).

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零度萤火

3楼-- · 2019-01-02 17:46

Personally, I ended up writing an InnerXml extension method using the Aggregate method:

public static string InnerXml(this XElement thiz)
{
   return thiz.Nodes().Aggregate( string.Empty, ( element, node ) => element += node.ToString() );
}

My client code is then just as terse as it would be with the old System.Xml namespace:

var innerXml = myXElement.InnerXml();

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宁负流年不负卿

4楼-- · 2019-01-02 17:47

With all due credit to those who discovered and proved the best approach (thanks!), here it is wrapped up in an extension method:

public static string InnerXml(this XNode node) {
    using (var reader = node.CreateReader()) {
        reader.MoveToContent();
        return reader.ReadInnerXml();
    }
}

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弹指情弦暗扣

5楼-- · 2019-01-02 17:52

I ended up using this:

Body = t.Element("body").Nodes().Aggregate("", (b, node) => b += node.ToString());

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ら面具成の殇う

6楼-- · 2019-01-02 18:00

Wondering if (notice I got rid of the b+= and just have b+)

t.Element( "body" ).Nodes()
 .Aggregate( "", ( b, node ) => b + node.ToString() );

might be slightly less efficient than

string.Join( "", t.Element.Nodes()
                  .Select( n => n.ToString() ).ToArray() );

Not 100% sure...but glancing at Aggregate() and string.Join() in Reflector...I think I read it as Aggregate just appending a returning value, so essentially you get:

string = string + string

versus string.Join, it has some mention in there of FastStringAllocation or something, which makes me thing the folks at Microsoft might have put some extra performance boost in there. Of course my .ToArray() call my negate that, but I just wanted to offer up another suggestion.

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查无此人

7楼-- · 2019-01-02 18:02

Keep it simple and efficient:

String.Concat(node.Nodes().Select(x => x.ToString()).ToArray())

Aggregate is memory and performance inefficient when concatenating strings
Using Join("", sth) is using two times bigger string array than Concat... And looks quite strange in code.
Using += looks very odd, but apparently is not much worse than using '+' - probably would be optimized to the same code, becase assignment result is unused and might be safely removed by compiler.
StringBuilder is so imperative - and everybody knows that unnecessary "state" sucks.

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