private void AssertPositionsAreCorrect(Point2D endPos, Point2D startPos)
{
Preconditions.Assert(!Equals(startPos, endPos), string.Format("Start pos {0} and end pos {1} of margin can't be the same", startPos, endPos));
Preconditions.Assert(startPos.X == endPos.X || startPos.Y == endPos.Y,
string.Format("Start pos {0} and end pos {1} are not horizontal nor vertical", startPos, endPos));
}