[英]How can I compose this LINQ expression?
我正在创建一个 web 应用程序来管理飞行学校,并且我具有以下数据库结构(不相关的表格已被模糊,相关表格已被翻译成英文以清楚起见):
我有一个表格截止日期,其中存储与飞机相关的所有截止日期。 此表链接到Aircrafts表。 然后我有一个OwnedAircrafts表,其中存储了飞机和人员的 ID(因为一个人可以拥有几架飞机或其中的一部分)。
我的问题是:
给定一个人的 id,我如何检索与他/她的飞机相关的截止日期列表? (最好使用方法语法)
换句话说:
下面的代码现在返回所有飞机的最后期限,无论所有者是谁。 如何参考OwnedAircrafts表以仅过滤与personId相关的截止日期?
IEnumerable<DeadlineViewModel> GetDeadlinesOfAPerson(long personId)
{
return _context.Deadlines
.Select(deadline => new DeadlineViewModel
{
Id = deadline.Id,
Aircraft = deadline.Aircraft,
Model = deadline.AircraftsNavigation.Model,
IdDeadlineType = deadline.DeadlineType,
DeadlineType = deadline.DeadlineTypesNavigation.Description
// other fields...
});
先感谢您!
尝试以下操作:
IEnumerable<DeadlineViewModel> GetDeadlinesOfAPerson(long personId)
{
return _context.Deadlines
.Where(x => x.deadline.ID == 12345)
.Select(deadline => new DeadlineViewModel
{
Id = deadline.Id,
Aircraft = deadline.Aircraft,
Model = deadline.AircraftsNavigation.Model,
IdDeadlineType = deadline.DeadlineType,
DeadlineType = deadline.DeadlineTypesNavigation.Description
// other fields...
});
遵循这种方法:
IEnumerable<DeadlineViewModel> GetDeadlinesOfAPerson(long personId)
{
return _context
.OwnedAircarfs
.Where( s => s.Persona == YourPersonId)
.Includes(s=> s.AirCrafts)
.ThenIncludes(s=> s.Deadlines)
.Select(deadline => new DeadlineViewModel
{
//use navigation properties to get value of related tables
// other fields...
}).ToList();
您可以将导航属性添加到您的实体,然后尝试这样的事情:
var user = _context.Users
.Include(user => user.OwnedAircrafts)
.ThenInclude(ownedAircraft => ownedAircraft.Aircraft)
.ThenInclude(aircraft => aircraft.Deadlines)
.FirstOrDefault(user => user.Id == userId)
return user.OwnedAircrafts
.SelectMany(ownedAircraft => ownedAircraft.Aircraft.Deadlines);
您不需要查询 Persons 表,因为OwendAircrafts
中提供了人员 ID
IEnumerable<DeadlineViewModel> GetDeadlinesOfAPerson(long personId)
{
return _context.Deadlines
.Where(deadline =>
deadline.Aircraft.OwnedAircrafts.Any(oa => oa.persona == personId))
.Select(deadline => new DeadlineViewModel
{
Id = deadline.Id,
Aircraft = deadline.Aircraft,
Model = deadline.AircraftsNavigation.Model,
IdDeadlineType = deadline.DeadlineType,
DeadlineType = deadline.DeadlineTypesNavigation.Description
// other fields...
});
}
这假设您在Aircraft
中有一个导航属性OwnedAircrafts
。
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