實體框架查詢檢查

Question

請使用以下腳本來創建表。我正在使用Entity Framework 3.5，當我創建一個edmx文件時，我沒有在Nodes表中看到ParentID列...爲什麼？因爲這我不能執行這個查詢Dim categories = From c In context.Nodes Where (c.ParentID = "1")我得到一個錯誤ParentID is not a member of HagglerModel.Nodes

 if exists(select name from sysobjects where name = 'NodeInsert' and type = 'tr') 
     drop trigger NodeInsert 
    go 

    if exists(select name from sysobjects where name = 'NodeUpdate' and type = 'tr') 
     drop trigger NodeUpdate 
    go 

    if exists(select name from sysobjects where type = 'u' and name = 'Tree') 
     Drop table Tree 
    go 

    if exists(select name from sysobjects where type = 'u' and name = 'Node') 
     Drop table Node 
    go 

    create table Node(
     NodeId int not null, 
     ParentId int null, 
     NodeName varchar(255) not null, 
     constraint PK_Node primary key(NodeId), 
     constraint UK_NodeName unique(NodeName) 
    ) 
    go 

    create table Tree(
     NodeId int not null, 
     ParentId int not null, 
     Level int not null, 
     constraint PK_Tree primary key(NodeId, ParentId), 
     constraint UK_Level unique(NodeId, Level) 
    ) 
    go 

    alter table Node 
     add constraint FK_NodeNode foreign key(ParentId) references Node(NodeId) --on delete cascade 
    go 

    alter table Tree 
     add constraint FK_NodeTreeNode foreign key(NodeId) references Node(NodeId) on delete cascade 
    go 

    --alter table Tree 
    -- add constraint FK_NodeTreeParent foreign key(ParentId) references Node(NodeId) on delete cascade 
    --go 

    create trigger NodeInsert on Node for insert as 
    begin 
     set nocount on 

     insert into Tree(NodeId, ParentId, Level) 
     select NodeId, NodeId, 0 
     from inserted 

     insert into Tree(NodeId, ParentId, Level) 
     select n.NodeId, t.ParentId, t.Level + 1 
     from inserted n, Tree t 
     where n.ParentId = t.NodeId 
    end 
    go 

    create trigger NodeUpdate on Node for update as 
    if update(ParentId) 
    begin 
     set nocount on 

     declare @child table(NodeId int, Level int) 

     insert into @child(NodeId, Level) 
     select t.NodeId, t.Level 
     from inserted n, Tree t 
     where n.NodeId = t.ParentId and t.Level > 0 

     delete Tree 
     where 
      Tree.NodeId in(select NodeId from @child) 
      and Tree.ParentId in(
       select t.ParentId 
       from inserted n, Tree t 
       where n.NodeId = t.NodeId and t.Level > 0 
      ) 

     delete Tree 
     where Tree.NodeId in(select NodeId from inserted) and Tree.Level > 0 

     insert into Tree(NodeId, ParentId, Level) 
     select n.NodeId, t.ParentId, t.Level + 1 
     from inserted n, Tree t 
     where n.ParentId = t.NodeId 

     insert into Tree(NodeId, ParentId, Level) 
     select c.NodeId, t.ParentId, t.Level + c.Level 
     from inserted n, Tree t, @child c 
     where n.NodeId = t.NodeId and t.Level > 0 
    end 
    go 

    insert into Node(NodeId, ParentId, NodeName) values(1, null, 'A') 
    insert into Node(NodeId, ParentId, NodeName) values(2, 1, 'B') 
    insert into Node(NodeId, ParentId, NodeName) values(3, 1, 'C') 
    insert into Node(NodeId, ParentId, NodeName) values(4, 2, 'D') 
    insert into Node(NodeId, ParentId, NodeName) values(5, 4, 'E') 
    insert into Node(NodeId, ParentId, NodeName) values(6, 4, 'F') 
    insert into Node(NodeId, ParentId, NodeName) values(7, 6, 'G') 
    select * from Node 
    select * from Tree 

    --gets all descendants of the Node 2 
    select c.* 
    from Node n, Tree t, Node c 
    where n.NodeName='B' 
     and n.NodeId = t.ParentId 
     and t.NodeId = c.NodeId 

    --gets path to the root from node 7 
    select p.* 
    from Node n, Tree t, Node p 
    where n.NodeName='G' 
     and n.NodeId = t.NodeId 
     and t.ParentId = p.NodeId 

    --changes parent of node 4 from 2 to 1 
    update Node set ParentId = 1 where NodeId = 4 
    select * from Node 
    select * from Tree 

Answer 1

在你的情況，我想的ParentId，可能是一個外鍵。您無法直接訪問外鍵。

這裏是一個職位，如何實現它.. Entity Framework: Setting a Foreign Key Property