Returns a pretty print string of a given XML string, with escape characters added in for invalid chars.

xml_prettyprint.cs

/// <summary>
/// Formats a given string into pretty print XML.
/// </summary>
private string FormatXml(string xml)
{
    try
    {
        XDocument doc = XDocument.Parse(xml);

        //Get the string representation out.
        string indentedXml = doc.ToString();
        var xmlBuilder = new StringBuilder(indentedXml);

        //Try to format the Regex strings.
        var matches = Regex.Matches(indentedXml, "<string>[^\r\n]*</string>");
        foreach (Match match in matches)
        {
            //Get the string out, XML format it.
            string regex = match.Value.Replace("<string>", "").Replace("</string>", "");
            regex = SecurityElement.Escape(regex);
            regex = "<string>" + regex + "</string>";

            xmlBuilder.Remove(match.Index, match.Length);
            xmlBuilder.Insert(match.Index, regex);
        }

        //Return the XML.
        return xmlBuilder.ToString();
    }
    catch (Exception e)
    {
        //Failed, just return normal XML.
        Error.Compile("Failed to generate valid Textmate file: '" + e.Message + "'.");
        return null;
    }
}