將SQL轉換爲Linq查詢

Question

我在Linq查詢方面很新穎，我只是想將我的數據庫查詢轉換成Linq。

這裏是我的簡單的SQL查詢：

var query = "SELECT EnrollmentDate, COUNT(*) AS StudentCount " 
      + "FROM Person " 
      + "WHERE EnrollmentDate IS NOT NULL " 
      + "GROUP BY EnrollmentDate"; 

var data = db.Database.SqlQuery<EnrollmentDateGroup>(query); 

這是工作正常，但怎麼可能有可能寫Linq中此查詢，我只是不能在group by語句轉換成Linq的。轉換成Linq似乎有點棘手。

任何人都可以幫助我嗎？

Answer 1

var result = db.Person 
       .Where(r=> r.EnrollmentDate != null) 
       .GroupBy(r=> r.EnrollmentDate) 
       .Select(group=> new 
           { 
           EnrollmentDate = group.Key, 
           Count = group.Count() 
           }); 

Answer 2

var query = from row in db.Person 
      where row.EnrollmentDate != null 
      group row by row.EnrollmentDate into grp 
      select new { 
       EnrollmentDate = grp.Key, 
       Count = grp.Count() 
      };