Linq 通过具有

有人能告诉我如何使用LINQtoSQL编写查询吗 搜索在特定州至少有一个场馆的郊区

位置

SuburbID
SuburbName
StateName

地点

编辑：最终答案：

如果您在地点/地点之间设置了外键：

string stateName = "New York";  

var locations = from loc 
                in dataContext.Locations 
                where loc.Venues.Count > 1 && loc.StateName == stateName 
                select loc;

---

如果不存在外键关系：

string stateName = "New York";

var locations = (from v 
                 in dataContext.Venues 
                 where v.StateName == stateName 
                 select (from l 
                         in dataContext.Locations 
                         where l.SuburbName == v.SuburbName && l.StateName == v.Statename              
                         select l
                        ).Single()).Distinct();

---

---

不过，你真的应该把桌子修好。会议桌上应该有一个suburbID，而不是“StateName”和“suburbID Name”-保留这两个名称是多余的。

以下是几个简单的答案：

var suburbNames = dataContext.Venues
  .Where(v => v.StateName == specificState)
  .GroupBy(v => v.SuburbName)
  .Select(g => g.Key)

           //

var locations = dataContext.Location
  .Where(loc => loc.StateName == specificState)
  .Where(loc => loc.Venues.Any())

---

使用该Vinces属性：您可以通过在linq to sql designer中添加关系来实现这一点，即使外键在数据库中不存在/未强制执行。

我知道该表应该有SuburbID，但有时用户可能会输入SuburbID，但它还不在数据库中？如果它还不在数据库中，请在插入之前添加它场地。或者让用户先输入一个新的郊区，然后再向其中添加一个场馆。假设用户完全输入了一个场馆的信息-此时，您有足够的信息来存储郊区。（除非有我们看不到的字段）。

string stateName = "New York";

var locations = (from v 
                 in dataContext.Venues 
                 where v.StateName == stateName 
                 select (from l 
                         in dataContext.Locations 
                         where l.SuburbName == v.SuburbName && l.StateName == v.Statename              
                         select l
                        ).Single()).Distinct();

var suburbNames = dataContext.Venues
  .Where(v => v.StateName == specificState)
  .GroupBy(v => v.SuburbName)
  .Select(g => g.Key)

           //

var locations = dataContext.Location
  .Where(loc => loc.StateName == specificState)
  .Where(loc => loc.Venues.Any())