private ColumnMapping FindOrCreateColumnMapping(EdmProperty column)
        {
            var columnMapping = _columns.SingleOrDefault(c => c.Column == column);
            if (columnMapping == null)
            {
                columnMapping = new ColumnMapping(column);
                _columns.Add(columnMapping);
            }

            return columnMapping;
        }
        private ColumnMapping FindOrCreateColumnMapping(DbTableColumnMetadata column)
        {
            var columnMapping = _columns.SingleOrDefault(c => c.Column == column);
            if (columnMapping == null)
            {
                columnMapping = new ColumnMapping(column);
                _columns.Add(columnMapping);
            }

            return columnMapping;
        }