如何将linq查询转换为非查询表达式？

Question

我使用EF6，我有这个linq到实体查询：

   from s in SensorObservationEntities.SensorsMeasures
            group s by s.SensorUnitId into g
            let latest = g.OrderByDescending(s => s.MeasureDate).FirstOrDefault()
            select latest

如何将其传递给非查询表达式？

Answer 1

你的意思是方法语法：

SensorObservationEntities.SensorsMeasures.GroupBy(g => g.SensorUnitId)
             .Select(y => y.OrderByDescending(x => x.MeasureDate).FirstOrDefault());

Answer 2

如果要将其转换为方法语法版本，可以逐步执行此操作。我喜欢从最后开始，一直到最开始：

1. select到Select定义来源：

   .Select(g => g.OrderByDescending(s => s.MeasureDate).FirstOrDefault());
   

2. group是GroupBy：

   .GroupBy(s => s.SensorUnitId)
   .Select(g => g.OrderByDescending(s => s.MeasureDate).FirstOrDefault());
   

3. from来源

   SensorObservationEntities.SensorsMeasures
   .GroupBy(s => s.SensorUnitId)
   .Select(g => g.OrderByDescending(s => s.MeasureDate).FirstOrDefault());