转换条件加盟SQL到LINQ

Question

我在SQL中是正常看似简单的查询：

SELECT table1.Id, count(table2.col) AS OrderCol 
FROM table1 
LEFT JOIN table2 ON table1.Id = table2.Id 
LEFT JOIN table3 ON table2.Id = table3.Id AND table2.condition = 3 //some integer value 
GROUP BY table1.Id 
ORDER BY count(table2.col) DESC 

当AND子句中加入出现，我不知道如何将其转换为LINQ ..

如何实现它？

Answer 1

试试这个：

var answer = (from t1 in table1 
      join t2 in table2 on t1.Id equals t2.Id into subData1 
      from t2sub in subData1.DefaultIfEmpty() 
      join t3 in table3 on new { Id = t2sub == null ? 0 : t2sub.Id, condition = t2sub == null ? 0 : t2sub.condition } equals new { t3.Id, condition = 3 } into subData 
      from t3sub in subData.DefaultIfEmpty() 
      group new { t1, t2sub } by t1.Id into subGroup 
      orderby subGroup.Count(x => x.t2sub != null) descending 
      select new { 
       Id = subGroup.Key, 
       OrderCol = subGroup.Count(x => x.t2sub != null) 
      }).ToList(); 

Answer 2

它去是这样的：

from t1 in db.Table1 
join t2 in db.Table2 on t1.field equals t2.field 
select new { t1.field2, t2.field3}