LINQ的最后一条记录 [英] last record in LINQ

问题描述

大家好

如何使用LINQ方法从数据库中检索最后一条记录?如果LINQ表没有记录，该如何处理错误?

Hi All

How can i retrieve the last record from database using LINQ method? And how a handle the error if the LINQ table has no records?

推荐答案

只需调用如果您认为表格有可能是空的，请使用

If you think there is a chance your table may be empty, use LastOrDefault()[^] instead. This will return null if nothing is found.

var lastItem = yourQuery.LastOrDefault();
if(lastItem == null)
{
    //Table was empty.
}

很显然，如果您的查询实际上未按任何顺序排序，则最后一个"项目可以为任何内容.

Obviously, if your query isn''t actually ordered by anything, then the "last" item could be anything.

最后一条记录:

1. 参见此 [请参见 [

For last record :

1. See This[^] (the answer is below the advertisements at this link, you will have to scroll a lot).

2. See This[^]

To handle the error, if table has no records:

Its just on the top of my head, i cant check it at present, so syntax error may be there:

if(tablename.Records.Count >0) //something like this will do
    {
         //write your code
    }

或

参见 [ ^ ]


顺便说一句，您通过谷歌搜索可能节省了您和我很多的时间.
(如果我有帮助，请接受回答或投票)

Anurag

OR

See this[^]


BTW, some googling by you may have saved your and mine lots of time.
(Please accept answer or provide votes if I was helpful)

Anurag

数据库在技术上是无序的(OK记录几乎按其进入的顺序出现，但这并不能保证)，因此，如果您需要特定的顺序，则必须添加一些执行此操作的方式(身份列(例如，整数代理键上的列)，自定义排序列，日期列等).
如果这样做，您只需要linq即可获取包含订购列的最大值"的记录:如何:在数字序列中找到最大值
[ ^ ].
请注意，如果没有记录，就不会有任何错误:除非您调用Single()，否则条目列表将只是空的，在这种情况下，SingleOrDefault()会更好，并检查默认"

DBs are technically unordered (OK records pretty much come out in the order they went in, but this isn''t guaranteed) so if you need a specific order, you must add some way to do this (identity column [e.g. on an integer surrogate key], a custom ordering column, date column etc).
If you do this, you just need the linq to get the record containing the Max value for your ordering column: How to: Find the Maximum Value in a Numeric Sequence
[^].
Note that there should not be any errors if you have no records: the list of entries will merely be empty, unless you call Single(), in which case SingleOrDefault() will be better, and check for "default"

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