GetXElementNames.cs

private IEnumerable<string> GetElementNames(XElement xElement, string path)
{
    var output = new List<string>();

    if (string.IsNullOrWhiteSpace(path))
    {
        path = xElement.Name.ToString();
        output.Add(path);

        if (xElement.HasAttributes)
        {
            output.AddRange(GetAttributesName(xElement, path));
        }
    }

    foreach (XElement element in xElement.Elements())
    {
        string name = element.Name.ToString();
        string fullName = path + "/" + name;

        output.Add(fullName);

        if (element.HasAttributes)
        {
            output.AddRange(GetAttributesName(element, path));
        }

        if (!element.HasElements)
        {
            continue;
        }
        output.AddRange(GetElementNames(element, fullName));
    }

    return output.OrderBy(o => o);
}

private IEnumerable<string> GetAttributesName(XElement xElement, string path)
{
    IEnumerable<string> output = xElement.Attributes()
                                         .Select(e => string.Format("{0}/{1}", path, e.Name.ToString()));
    return output;
}