System.Data.ConstraintEnumerator.GetNext C# (CSharp) Method

        public bool GetNext()
        {
            Constraint candidate;
            _currentObject = null;
            while (_tables != null)
            {
                if (_constraints == null)
                {
                    if (!_tables.MoveNext())
                    {
                        _tables = null;
                        return false;
                    }
                    _constraints = ((DataTable)_tables.Current).Constraints.GetEnumerator();
                }

                if (!_constraints.MoveNext())
                {
                    _constraints = null;
                    continue;
                }

                Debug.Assert(_constraints.Current is Constraint, "ConstraintEnumerator, contains object which is not constraint");
                candidate = (Constraint)_constraints.Current;
                if (IsValidCandidate(candidate))
                {
                    _currentObject = candidate;
                    return true;
                }
            }
            return false;
        }

        internal void EnableConstraints()
        {
            IntPtr hscp;
            Bid.ScopeEnter(out hscp, "<ds.DataSet.EnableConstraints|INFO> %d#\n", ObjectID);
            try {
                bool errors = false;
                for (ConstraintEnumerator constraints = new ConstraintEnumerator(this); constraints.GetNext(); ) {
                    Constraint constraint = (Constraint)constraints.GetConstraint();
                    errors |= constraint.IsConstraintViolated();
                }

                foreach (DataTable table in Tables) {
                    foreach (DataColumn column in table.Columns) {
                        if (!column.AllowDBNull) {
                            errors |= column.IsNotAllowDBNullViolated();
                        }
                        if (column.MaxLength >= 0) {
                            errors |= column.IsMaxLengthViolated();
                        }
                    }
                }

                if (errors)
                    this.FailedEnableConstraints();
            }
            finally {
                Bid.ScopeLeave(ref hscp);
            }
        }