将SQL转换为Linq查询

Question

我是Linq查询的新手，我只是想将我的DB查询转换为Linq。

下面是我的简单SQL查询:

var query = "SELECT EnrollmentDate, COUNT(*) AS StudentCount "
          + "FROM Person "
          + "WHERE EnrollmentDate IS NOT NULL "
          + "GROUP BY EnrollmentDate";
var data = db.Database.SqlQuery<EnrollmentDateGroup>(query);

它是工作得很好，但是怎么可能在Linq中编写这个查询，我只是不能将group by语句转换为Linq。转换成Linq似乎有点棘手。

有谁能帮我一下吗?

Answer 1

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()
            };

Answer 2

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