c# - 将 sql 转换为 LINQ TOP 1 NOT in

Question

如何将此 SQL 转换为 LINQ？

Select Top 1 iD, Grad from tbl1 
WHERE tbl1.ID not in 
(Select GradId from tbl2 WHERE ID = 99469)

Answer 1

看起来最简单的方法是这样的：

var grads = 
    (from r in tbl2 
     where r.ID == 99469 
     select r.GradID);
var results = 
    (from r in tbl1
     where !grads.Contains(r.ID)
     select new { r.ID, r.Grad })
    .FirstOrDefault();

或者更简洁一点：

var grads = ...
var results = tbl1
    .Select(r => new { r.ID, r.Grad })
    .FirstOrDefault(r => !grads.Contains(r.ID));

Answer 2

类似的东西：

 var query =
         (from c in db.tbl1
          where !(from d in db.tbl2
          select d.id)
               .Contains(c.id)
          select c).Take(1)