c# - 如何从 LINQ 实现 SQL CASE 语句

Question

我是 LINQ 的新手，我想知道我是否可以从 LINQ 实现以下 SQL 查询？

我正在使用 Entity Framework Core。

SELECT 0 [All], [Range] =
    CASE  
        WHEN Value BETWEEN 0 AND 25 THEN 'Low' 
        WHEN Value BETWEEN 25 AND 75 THEN 'Medium' 
        WHEN Value BETWEEN 75 AND 90 THEN 'High' 
        WHEN Value BETWEEN 90 AND 100 THEN 'Very High' 
    END 
FROM Result.Calculation C 
    INNER JOIN Data.SampleSet S ON C.SampleSetID = S.ID  
WHERE  S.SampleDrawn >= DATEADD(MONTH,-3,GETDATE()) AND S.Department = 'LOCATION A'

目前，我正在使用如下所示的 FromSql 来调用存储过程。我想知道我是否可以在不使用存储过程的情况下做同样的事情？

var result = context.MyData.FromSql("data.GetMyData @pType = {0}, @pLocation = {1}, @pNoOfDays = {2}, @pStartDate = {3}, @pEndDate = {4}", type, location, noOfDays, startDate, endDate).ToList();

谢谢。

Answer 1

你可以使用它。

from C in Calculations
join S in SampleSets on C.SampleSetID equals S.ID 
where S.SampleDrawn >= DateTime.Now.AddMonths(-3)
      && S.Department == "LOCATION A"
select new {
    All = 1 
    , Range = 
        (C.Value >= 0 && C.Value < 25) ? "Low" :
        (C.Value >= 25 && C.Value < 75) ? "Medium" :
        (C.Value >= 75 && C.Value < 90) ? "High" :
        (C.Value >= 90 && C.Value <= 100) ? "Very High" : null
}