private void InstallConstraint(IConstraint constraint) { foreach (IModelView view in _handler.ActiveViews) { if (view != null) { IConstraint viewConstraint = constraint.InstallInView(view); List <IConstraint> viewConstraintList; viewConstraints.TryGetValue(view, out viewConstraintList); if (viewConstraintList == null) { viewConstraintList = viewConstraints[view] = new List <IConstraint>(); } viewConstraintList.Add(viewConstraint); } } }