用导航属性替换联接

如何解决用导航属性替换联接

根据这里人们的建议，我正在尝试使用导航属性重写下面的linq查询。

我还没走很远，因为我不确定如何用导航属性替换Linq查询中的联接。

到目前为止，我有这个：

await _context.StarList(sl => new 
{
    sl.StarId,sl.StarType,sl.StarTitle,sl.ChemicalId...
}

但是，在原始查询中，我开始在查询中使用“ chemicalatoms”。

所以我不确定如何过渡到他们。

所以我的问题是，如何用导航属性替换原始查询中的联接？

谢谢！

 public async Task<ActionResult<object>> GetStarChemicalData(string starID)
    {
        var starChemicalData = await (from starlist in _context.StarList
                                      join ql in _context.ChemicalList on starlist.ChemicalId equals ql.ChemicalId into stars
                                      from chemicallist in stars.DefaultIfEmpty()
                                      join qc in _context.ChemicalAtoms on chemicallist.ChemicalId equals qc.ChemicalId into chemicals
                                      from chemicalatoms in chemicals.DefaultIfEmpty()
                                      join nk in _context.StarLinks on chemicalatoms.AtomId equals nk.AtomId into links
                                      from starlinks in links.DefaultIfEmpty()
                                      where starlist.StarId == starID
                                      select new
                                      {
                                          StarId = starlist.StarId,StarType = starlist.StarType,StarTitle = starlist.StarTitle,ChemicalId = starlist.ChemicalId,AtomId = (Guid?)chemicalatoms.AtomId,OrderId = chemicalatoms.OrderId,ChemicalText = chemicallist.ChemicalText,AtomText = chemicalatoms.AtomText,Wavelength = chemicalatoms.Wavelength,isRedShifted = (starlinks.AtomId != null && starlist.StarType == 1) ? 1
                                          : (starlinks.AtomId == null && starlist.StarType == 1) ? 0
                                          : (int?)null
                                      })
                                          .GroupBy(x => x.StarId)
                                          .Select(g => new
                                          {
                                              StarId = g.FirstOrDefault().StarId,StarType = g.FirstOrDefault().StarType,StarTitle = g.FirstOrDefault().StarTitle,ChemicalId = g.FirstOrDefault().ChemicalId,ChemicalText = g.FirstOrDefault().ChemicalText,ChemicalAtoms = (g.FirstOrDefault().AtomId != null ? g.Select(x => new
                                              {
                                                  AtomId = x.AtomId,OrderId = x.OrderId,AtomText = x.AtomText,Feedback = x.Wavelength,IsCorrect = x.isRedShifted
                                              }) : null)
                                          }).FirstOrDefaultAsync();

        return starChemicalData;
        

解决方法

根据以上交流成功，我想我可以总结一下结果，在这里）） 所以，不要这样：

$('.testimonial_slider').owlCarousel({
    loop:false,margin:32,nav:false,dots: true,items:1,mouseDrag: false,dotsData: true,});

我们可以拥有这个：

var starChemicalData = await (from starlist in _context.StarList
    join ql in _context.ChemicalList on starlist.ChemicalId equals ql.ChemicalId into stars
    from chemicallist in stars.DefaultIfEmpty()
    join qc in _context.ChemicalAtoms on chemicallist.ChemicalId equals qc.ChemicalId into chemicals
    from chemicalatoms in chemicals.DefaultIfEmpty()
    join nk in _context.StarLinks on chemicalatoms.AtomId equals nk.AtomId into links 
    ...
    );

---

请注意，使用Include时最重要的是应在此处使用的数据库表之间适当地设置关系（主外键）。

另一个重要的事情是，如果您的PK⟶FK关系中的一个包含_context.StarList.Include(st => st.ChemicalList) .Include(ca => ca.ChemicalAtoms) // or ThenInclude,based on your relations .Include(sl => sl.StartLinks) ... Select(r => new {...}) ... 的值，而实际上不应该包含Include()，则null不会带来行结果。