Unicode Regex; Invalid XML characters

Question

The list of valid XML characters is well known, as defined by the spec it\'s:

#x9 | #xA | #xD | [#x20-#xD7FF] | [#xE000-#xFFFD] | [#x10000-#x10FFFF]
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Answer 1

I know this isn't exactly an answer to your question, but it's helpful to have it here:

Regular Expression to match valid XML Characters:

[\u0009\u000a\u000d\u0020-\uD7FF\uE000-\uFFFD]

So to remove invalid chars from XML, you'd do something like

// filters control characters but allows only properly-formed surrogate sequences
private static Regex _invalidXMLChars = new Regex(
    @"(?
/// removes any unusual unicode characters that can't be encoded into XML
/// 
public static string RemoveInvalidXMLChars(string text)
{
    if (string.IsNullOrEmpty(text)) return "";
    return _invalidXMLChars.Replace(text, "");
}

I had our resident regex / XML genius, he of the 4,400+ upvoted post, check this, and he signed off on it.