private Change Inc(string part)
{
var val = Get(part);
var change = new Change
{
From = val,
To = ++val
};
Set(part, change.To);
return change;
}
private Change Set(XElement elem, int val)
{
var attr = elem.Attribute("value");
var change = new Change { From = Get(attr), To = val };
attr.SetValue(val);
return change;
}