public void SetAsFirstPage(string pageId, string sectionId)
{
var sectionXml = GetChildrenScopeHierarchy(sectionId);
var xDoc = XDocument.Parse(sectionXml);
XNamespace xNs = xDoc.Root.Name.Namespace;
var sectionElement = xDoc.Elements(xNs + "Section")
.Single(x => x.Attribute("ID").Value.Equals(sectionId));
var pageElements = sectionElement.Elements(xNs + "Page");
if (pageElements.Count() > 1)
{
var page = pageElements.Single(x => x.Attribute("ID").Value.Equals(pageId));
page.Remove();
sectionElement.Elements(xNs + "Page").FirstOrDefault().AddBeforeSelf(page);
_mApp.UpdateHierarchy(xDoc.ToString());
}
}