[英]How can I make a JOIN query with LINQ between two tables (entities) with many-to-many relationship, while there is no joining table in EF?
[英]EF Core Query between two join entities
我有以下實體:
並遵循多對多聯接實體:
工作和志願者都有多個人才。 我想搜索所有喬布斯,他們的人才與志願者的才能相同。
我怎樣才能做到這一點? 目前我正在使用以下代碼,但結果我獲得了包含一個(或多個)所需天賦的所有作業。 我想只找到志願者(至少)所有必需人才的工作。
public async Task<IActionResult> FindJobs(int? id)
{
if (id == null)
{
return NotFound();
}
var volunteer = await _context.Volunteers
.Include(v => v.TalentVolunteers)
.ThenInclude(v => v.Talent)
.FirstOrDefaultAsync(m => m.VolunteerID == id);
if (volunteer == null)
{
return NotFound();
}
var jobs = new List<Job>();
var talentVolunteers = new HashSet<int>(volunteer.TalentVolunteers.Select(t => t.TalentID));
foreach (var talent in _context.JobTalents)
{
if (talentVolunteers.Contains(talent.TalentID))
{
var selectedJob = _context.Jobs
.Include(t => t.JobTalents)
.ThenInclude(v => v.Talent)
.SingleOrDefault(t => t.JobID == talent.JobID);
jobs.Add(selectedJob);
}
}
var volunteersFindJobsViewModel = _mapper.Map<Volunteer, VolunteersFindJobsViewModel>(volunteer);
volunteersFindJobsViewModel.Jobs = jobs;
return View(volunteersFindJobsViewModel);
}
第一選擇
為志願者選擇所有人才ID並將其存儲在列表/數組中,然后在作業的條件語句中使用此列表
var volunteerTalentIds = _context.TalentVolunteer.Where(a=>a.VolunteerId == {yourVolunteerId}).Select(a=>a.TalentId).ToList();
var selectedJobs = _context.Jobs.Include(a=>a.JobTalents).Where(a=>a.JobTalents.All(b=>volunteerTalentIds.Contains(b.TalentId))).ToList();
第二選擇
做一連串的連接
var selectedJobs = (from job in _context.Jobs
join jobTalent in _context.JobTalents on jobTalent.JobId equals job.JobId
join volunteerTalent in _context.VolunteerTalents on jobTalent.TalentId equals volunteetTalent.TalentId
where volunteerTalent.VolunteerId = {yourVolunteerId} select job).ToList();
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