/// <summary>
/// 获取DataKey对应的长整形
/// </summary>
/// <param name="dataKey">DataKey</param>
/// <returns>dataKey不存在时返回0</returns>
public long GetLong(string dataKey)
{
//把所有数据（数据量不大）一次读取并存入缓存，从中获取dataKey
IEnumerable <SystemData> systemDatas = systemDataRepository.GetAll();
if (systemDatas == null)
{
return(default(long));
}
SystemData systemData = systemDatas.FirstOrDefault(n => n.Datakey == dataKey);
if (systemData == null)
{
return(default(long));
}
return(systemData.LongValue);
}