Question

我有以下模型和关系：

Table: Granddad
GranddadID
GranddadName

Table: Father
FatherID
GranddadID
FatherName

Table: Son
SonID
FatherID
SonName

爷爷控制器中的

：

public ActionResult Edit(int tmpgranddadid)
{
   var q = (from g in _e.Grandad
           where g.GrandadID == tmpgranddadid
           select g).FirstOrDefault();

   string son_name = q.Father.Son.SonName.ToString(); // <- is wrong, how to do this?

   return View(q);
}

如何从链接的链接表中检索值？

谢谢

Answer 1

也许你想要任何可能很多的儿子？

q.Fathers.First().Sons.First().SonName.ToString();

要小心，因为如果父亲没有儿子，First（）可以抛出异常。这将处理这种情况：

string sonName = null;
Father father = q.Fathers.FirstOrDefault();
if (father != null) {
    Son son = father.Sons.FirstOrDefault();
    if (son != null) {
        sonName = son.SonName.ToString();
    }
}

Answer 2

查看联接：

http://www.hookedonlinq.com/JoinOperator.ashx

Answer 3

假设您的数据源看起来像这样：

public class SomeDataSource
{
    public List<Granddad> Granddad;
    public List<Father> Father;
    public List<Son> Son;
}

假设你实际上是在孙子的第一个孙子之后那么：

var firstGrandson = (from son in _e.Son
               join father in _e.Father on son.FatherID equals father.FatherID
               join granddad in _e.Granddad on father.GranddadID equals granddad.GranddadID
               where granddad.GranddadID == tmpgranddadid
               select son).FirstOrDefault();

if (firstGrandson == null)
    throw new Exception("This granddad has no grandsons.");

string son_name = firstGrandson.SonName;

这是你需要的吗？

Linq - 从链接的链表中检索值

3 个答案: