Linq到SQL - 分组依据和计数 [英] Linq to SQL - Group By and Count

问题描述

我正在尝试转换此查询（已经工作）

  SELECT Building.NAME，COUNT（[User]。 ID）
 FROM BuildingUser 
 INNER JOIN Building ON Building.ID = BuildingUser.ID_BUILDING 
 INNER JOIN [User] ON [User] .ID = BuildingUser.ID_USER 
 GROUP BY Building。 NAME 
  

到Linq到SQL，但我不知道我做错了什么。看看我的尝试

 从db.GetTable< BuildingUser>（）中的buildinguser 
在db.GetTable中联接构建<构建>（）
在buildinguser.ID_BUILDING等于building.ID 
在db.GetTable中< User>（）中的用户
在buildinguser.ID_USER上等于user.ID 
组构建building.name into grpBuilding 
 select new 
 {
 building = grpBuilding.Key，
 users = 
}; 
  

我只需要分组我的建筑物，并计算每个人有多少用户。

$只需使用计数方法即可：

$ b

$ b

 来自在db.GetTable< BuildingUser>（）中的buildinguser 
在db.GetTable< Building>（）中联接构建buildingus.ID_BUILDING上的
等于building .ID 
在db.GetTable中加入用户< User>（）
在buildinguser.ID_USER上等于user.ID 
通过building.NAME将组构建为grpBuilding 
 select new 
 {
 building = grpBuilding.Key，
 users = grpBuilding.Count（）
}; 
  

I'm trying to convert this query (already working)

SELECT Building.NAME, COUNT([User].ID)
FROM BuildingUser
INNER JOIN Building ON Building.ID = BuildingUser.ID_BUILDING
INNER JOIN [User] ON [User].ID = BuildingUser.ID_USER
GROUP BY Building.NAME

To Linq to SQL, but I don't know what I'm doing wrong. Look at my trying

from buildinguser in db.GetTable<BuildingUser>()
join building in db.GetTable<Building>()
on buildinguser.ID_BUILDING equals building.ID
join user in db.GetTable<User>()
on buildinguser.ID_USER equals user.ID
group building by building.NAME into grpBuilding
select new
{
    building = grpBuilding.Key,
    users = 
};

I just need to group my Buildings and count how many users each one has.

解决方案

Simply use the the Count method:

from buildinguser in db.GetTable<BuildingUser>()
join building in db.GetTable<Building>()
on buildinguser.ID_BUILDING equals building.ID
join user in db.GetTable<User>()
on buildinguser.ID_USER equals user.ID
group building by building.NAME into grpBuilding
select new
{
    building = grpBuilding.Key,
    users = grpBuilding.Count()
};

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