/// <summary>
/// 使用已有的辅助类初始化 <see cref="Py.Sql.SqlHelper"/> 的新实例，新实例和参数使用同一个连接。
/// </summary>
/// <param name="helper">The helper。</param>
/// <exception cref="ArgumentNullException"><paramref name="helper" /> 为空。</exception>
/// <exception cref="ArgumentException">传递的辅助类和当前实例的类型不相同。</exception>
public MySqlHelper(DbHelper helper)
{
Thrower.ThrowArgumentNullExceptionIf(helper, "helper");
_connection = helper.Connection as MySqlConnection;
Thrower.ThrowArgumentExceptionIf(_connection == null, "连接空");
}