如何使用Linq到实体从列中检索最大的日期和时间？

Question

I have datetime column named DateMeasure in sql table.

I use entity framework 6 in my .net project.

Here is example of my table:

 Id           | NumberP  | TrackNumber | DateMeasure
28092|15240000|1.0.7.1782|2009040004731|2008-01-20 13:10:22.000
28094|61615000|1.0.7.1782|2009040007696|2010-05-20 13:11:38.000
28095|95317000|1.0.7.1782|2009040007695|2011-08-20 13:10:18.000
28101|15240000|1.0.7.1782|2009040004740|2015-11-20 14:10:22.000
28103|61615000|1.0.7.1782|2009040007690|2015-11-20 14:11:38.000
28104|95317000|1.0.7.1782|2009040007710|2009-02-20 14:10:18.000

The row that I want to get from table with help of Linq to entity:

28103|61615000|1.0.7.1782|2009040007690|2015-11-20 14:11:38.000

How can I retrieve the biggest(latest) date and time from the column using Linq to entity?

Answer 1

You can get the max date using Max extension:

var maxDate = context.Table.Max(m => m.DateMeasure);

Then, you can use FirstOrDefault to get that entity:

var model = context.Table.FirstOrDefault(m => m.DateMeasure == maxDate);

Actually, you can do it in just one query:

var model = context.Table.FirstOrDefault(m => m.DateMeasure == context.Table.Max(x => x.DateMeasure));

Answer 2

You can use the OrderBy methods of a IQuery object in Linq to sort by the DateMeasure column and fetch the first entry.

(from s in context.Table
       orderby s.DateMeasure descending).First()

Or with:

context.Table
       .OrderByDescending(s => s.DateMeasure)
       .First();

The OrderByDescending method will sort the query in descending order, you can also use OrderBy to sort by ascending order.