private void PropertyCollection_Inserted(int index, object value)
{
XmlNode form_prop;
form_prop = this.Node.SelectSingleNode("form:properties", this._document.NamespaceManager);
if (form_prop == null)
{
form_prop = _document.CreateNode("properties", "form");
}
FormProperty prop = value as FormProperty;
form_prop.AppendChild(prop.Node);
this.Node.AppendChild(form_prop);
}