用良好的 C# 语法编写简单布尔方法的最佳方法

Question

大家好，我好像到处都有这类方法。

下面的方法想要完成这些简单的任务：

1. 打开数据库连接（IntLMPDB 对象）
2. 从一个小的 DB 表中读取一条简单的记录（DB 表是用字符串作为键的，因为每个字符串都是方法的名称，所以我只想要表中的每个行），其余行是一系列时间戳告诉我事情发生的时间。
3. 如果找不到记录，则返回异常，因为无能为力。
4. 如果您找到该记录，请查看第二个日期（如果它完全丢失），然后设置为 true，因为这是第一次运行。
5. 如果第一个日期大于第二个日期，则最后还是要开始实际操作，因为它已更新，是时候运行了。否则，如果没有，请设置为 False，因为还没有更新。

所以这里是代码......我正在尝试做的是将其缩减为运行这些检查的最佳和最快的方法。我不关心数据库连接问题或类似问题。

    private static bool isLastIntervalNewerThanDB(string muiMethod)
    {
       using (var db = new IntLMPDB())
        {
            // Try to load a matching record.
            LastIntervalUpdated liRec = db.LastIntervalUpdateds.FirstOrDefault(rec => rec.method == muiMethod);
            // If it could not be loaded, exit because there's no way to determine if we should run.
             if (liRec == null) { throw new Exception(string.Format("Could NOT find LastIntervalUpdated record for muiMethod: {0}", muiMethod)); }
            else
            {
                // we have a valid interval record, so lets check that it has been updated since the last webPostTime.
                // put another way, there are three datetime values in the LastIntervalUpdated table. First is the
                // interval itself, second is the retrievalTime and third is the webPostTime. Whenever the MUI is 
                // checked for a new interval if one is found then the code updates the retrievalTime to the current
                // instant in time. This tells us what the last interval this application found on its last run was.
                // The thrid value is the webPostTime, this time instant is only updated by this very method we're in
                // right here. We can use this logic: if the retrievalTime is greater than the webPostTime then there's
                // a newer interval that we haven't yet processed and inserted into the databse. So we should run the
                // method below and update ALL of the syncable values into the databse. Then we'll set the dbPostTime to 
                // the current instance. As it goes, if this program then runs again before the interval is updated
                // then the dbPostTime will be greater than the retrieval time and we'll know to do nothig. Simple Right? :)

                // or check here includes a NULL check on dbPostTime because it's possible that dbPostTime is NULL,
                // in the example of the first time the system runs. It might have run a LastUpdate sync and not yet
                // done this method, so dbPostTime would be NULL. None of the other columns are allowed to be null.
                if (liRec.dbPostTime_EST == null || liRec.retrievalTime_EST > liRec.dbPostTime_EST)
                { return true; }
                else { return false; }
            }
       }
    }

Answer 1

我认为逻辑很好。我建议你做这样的事情来提高可读性*：

private static bool isLastIntervalNewerThanDB(string muiMethod)
{
   using (var db = new IntLMPDB())
    {
        LastIntervalUpdated liRec 
            = db.LastIntervalUpdateds
                    .FirstOrDefault(rec => rec.method == muiMethod);

        if (liRec == null) 
        { 
            throw new Exception(
                string.Format("Could NOT find LastIntervalUpdated record for muiMethod: {0}", muiMethod)); 
        }

        return liRec.dbPostTime_EST == null 
            || liRec.retrievalTime_EST > liRec.dbPostTime_EST;        
   }
}

*虽然可读性是主观的，但我认为if (liRec == null) 之后的else 只会添加不必要的嵌套，并且最终的条件可以折叠成单个表达式。也永远不要低估长表达式中放置良好的换行符 - 它可以在可读和不可读代码之间产生所有差异。

Answer 2

private static bool isLastIntervalNewerThanDB(string muiMethod)
    {
       using (var db = new IntLMPDB())
        {
            // Try to load a matching record.
            LastIntervalUpdated liRec = db.LastIntervalUpdateds.FirstOrDefault(rec => rec.method == muiMethod);
            // If it could not be loaded, exit because there's no way to determine if we should run.
             if (liRec == null) { 
                     throw new Exception(string.Format("Could NOT find LastIntervalUpdated record for muiMethod: {0}", muiMethod)); 
             }

                // we have a valid interval record, so lets check that it has been updated since the last webPostTime.
                // put another way, there are three datetime values in the LastIntervalUpdated table. First is the
                // interval itself, second is the retrievalTime and third is the webPostTime. Whenever the MUI is 
                // checked for a new interval if one is found then the code updates the retrievalTime to the current
                // instant in time. This tells us what the last interval this application found on its last run was.
                // The thrid value is the webPostTime, this time instant is only updated by this very method we're in
                // right here. We can use this logic: if the retrievalTime is greater than the webPostTime then there's
                // a newer interval that we haven't yet processed and inserted into the databse. So we should run the
                // method below and update ALL of the syncable values into the databse. Then we'll set the dbPostTime to 
                // the current instance. As it goes, if this program then runs again before the interval is updated
                // then the dbPostTime will be greater than the retrieval time and we'll know to do nothig. Simple Right? :)

                // or check here includes a NULL check on dbPostTime because it's possible that dbPostTime is NULL,
                // in the example of the first time the system runs. It might have run a LastUpdate sync and not yet
                // done this method, so dbPostTime would be NULL. None of the other columns are allowed to be null.

               return liRec.dbPostTime_EST == null 
                      || liRec.retrievalTime_EST > liRec.dbPostTime_EST;     

       }
    }

Answer 3

保留第一个 if 去掉第一个 else 并将最后一个压缩成一行 if/else

if (liRec == null) { throw new Exception(string.Format("Could NOT find LastIntervalUpdated record for muiMethod: {0}", muiMethod)); }

liRec.dbPostTime_EST == null || liRec.retrievalTime_EST > liRec.dbPostTime_EST ? return true : return false

Answer 4

我会将布尔逻辑移至 LastIntervalUpdated 类：

public class LastIntervalUpdated
{
    public bool IsLastIntervalNewer
    {
        get
        {
            return this.dbPostTime_EST == null || this.retrievalTime_EST > this.dbPostTime_EST
        }
    }
    //other properties...
}

然后你可以把注释放在更接近定义的地方。它还允许您将查询简化为：

private static bool isLastIntervalNewerThanDB(string muiMethod)
{
    using (var db = new IntLMPDB())
    {
        LastIntervalUpdated liRec = db.LastIntervalUpdateds.FirstOrDefault(rec => rec.method == muiMethod);
        if(liRec == null) throw new Exception(string.Format("Could NOT find LastIntervalUpdated record for muiMethod: {0}", muiMethod))
        return liRec.IsLastIntervalNewer;
    }
}

我还会考虑为失败的查找创建异常类型，例如 ObjectNotFoundException，而不是直接抛出 Exception。