MVC +EF+linq 多表联查

Posted 2020-06-14

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：

代码如下：

 

 1   var userListTest = (from u in db.Users
 2                                 join p in db.User_partB on u.userGUID
 3               equals p.userGUID
 4                                 join d in db.partBs on p.partID equals d.partID
 5                                 select new { name = u.userName, departName = d.partName });
 6             List<dynamic> oneList = new List<dynamic>();
 7             foreach (var one in userListTest.ToList())
 8             {
 9                 dynamic dyObject = new ExpandoObject();
10                 dyObject.userName = one.name;
11                 dyObject.departName = one.departName;
12                 oneList.Add(dyObject);
13             }
14             ViewBag.dyObject = oneList;
15             return View();

前台数据展现效果：

 1 <table>
 2     <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>
 3     @{foreach (var one in ViewBag.dyObject)
 4     {
 5         <tr>
 6             @*<td>@one.userLoginName</td>*@
 7             <td>@one.userName</td>
 8             @*<td>@one.active==1?"启用":"禁用"</td>*@
 9             <td>@one.departName</td>
10             <td></td>
11         </tr>
12     }
13     }
14 </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：

代码如下：

 1  var userListTest = (from u in db.Users
 2                                 join p in db.User_partB on u.userGUID
 3               equals p.userGUID into temp
 4                                 from t in temp.DefaultIfEmpty()
 5                                 join d in db.partBs on t.partID equals d.partID 
 6                                 into tempone
 7                                 from user in tempone.DefaultIfEmpty()
 8                                 select new { name = u.userName, departName = user.partName });
 9             List<dynamic> oneList = new List<dynamic>();
10             foreach (var one in userListTest.ToList())
11             {
12                 dynamic dyObject = new ExpandoObject();
13                 dyObject.userName = one.name;
14                 dyObject.departName = one.departName;
15                 oneList.Add(dyObject);
16             }
17             ViewBag.dyObject = oneList;
18             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。