Detect XML fragments in C#

Question

Is there a reliable way to detect in C#/.NET whether a given piece of XML is rooted XML content or a non-rooted fragment?

Rooted content:

<?xml version="1.0" encoding="UTF-8"?>
<root>
    <a>a</a>
</root>

Fragment:

<a>a</a>
<b>b</b>
<c>c</c>

I'm trying to identify these situations using the XmlReader and XDocument classes but I can't really distinguish between ordinary XmlExceptions and the one thrown when trying to load an otherwise valid fragment.

Answer 1

If you want to use XmlReader, you can do it like this:

static bool IsXmlRooted(Stream st) {
    bool sawRoot = false;
    using (var reader = XmlReader.Create(st, new XmlReaderSettings() {
        // fragment works for documents too
        ConformanceLevel = ConformanceLevel.Fragment
    })) {
        while (reader.Read()) {
            // if we see element at depth 0 - it's top-level element
            if (reader.NodeType == XmlNodeType.Element && reader.Depth == 0) {
                // if we already saw another top level element - that is fragment
                // can return fast
                if (sawRoot)
                    return false;
                sawRoot = true;
            }
        }
    }
    return true;
}