MVC +EF+linq 多表联查

时间:2023-12-31 10:12:20

关于linq的多表联查效果的实现:

后台多表查询  内连接:

SELECT
[Extent2].[partID] AS [partID],
[Extent1].[userName] AS [userName],
[Extent3].[partName] AS [partName]
FROM [dbo].[User] AS [Extent1]
INNER JOIN [dbo].[User_partB] AS [Extent2] ON [Extent1].[userGUID] = [Extent2].[userGUID]
INNER JOIN [dbo].[partB] AS [Extent3] ON [Extent2].[partID] = [Extent3].[partID]

数据库数据效果展示:

MVC +EF+linq  多表联查

代码如下:

   var userListTest = (from u in db.Users
join p in db.User_partB on u.userGUID
equals p.userGUID
join d in db.partBs on p.partID equals d.partID
select new { name = u.userName, departName = d.partName });
List<dynamic> oneList = new List<dynamic>();
foreach (var one in userListTest.ToList())
{
dynamic dyObject = new ExpandoObject();
dyObject.userName = one.name;
dyObject.departName = one.departName;
oneList.Add(dyObject);
}
ViewBag.dyObject = oneList;
return View();

前台数据展现效果:

 <table>
<tr><td>用户登录名</td><td>姓名</td><td>状态</td><td>角色</td><td>操作</td></tr>
@{foreach (var one in ViewBag.dyObject)
{
<tr>
@*<td>@one.userLoginName</td>*@
<td>@one.userName</td>
@*<td>@one.active==?"启用":"禁用"</td>*@
<td>@one.departName</td>
<td></td>
</tr>
}
}
</table>

linq  多表联查 外链接:

SELECT
1 AS [C1],
[Extent1].[userName] AS [userName],
[Extent3].[partName] AS [partName]
FROM [dbo].[User] AS [Extent1]
LEFT OUTER JOIN [dbo].[User_partB] AS [Extent2] ON [Extent1].[userGUID] = [Extent2].[userGUID]
LEFT OUTER JOIN [dbo].[partB] AS [Extent3] ON [Extent2].[partID] = [Extent3].[partID]

数据库数据展示效果:

MVC +EF+linq  多表联查

代码如下:

  var userListTest = (from u in db.Users
join p in db.User_partB on u.userGUID
equals p.userGUID into temp
from t in temp.DefaultIfEmpty()
join d in db.partBs on t.partID equals d.partID
into tempone
from user in tempone.DefaultIfEmpty()
select new { name = u.userName, departName = user.partName });
List<dynamic> oneList = new List<dynamic>();
foreach (var one in userListTest.ToList())
{
dynamic dyObject = new ExpandoObject();
dyObject.userName = one.name;
dyObject.departName = one.departName;
oneList.Add(dyObject);
}
ViewBag.dyObject = oneList;
return View();

前台数据展示效果同上

上述过程中,遇到  延迟加载后的动态数据,TOList()之后,传递到前台后,在foreach循环时,无法通过对象.属性的形式,读取出来,报“OBJECT未定义该属性”,经过查找原因发现,该动态数据为internal类型,只能同一程序集内访问,找了若干方法,不太适用,当然,如果大家有好的建议,可以一起交流讨论,究于当前场景,我选择了ExpandoObject,来动态处理,linq的查询结果。