Using LINQ to search relational databases

Question

I have the following databases:

and the following code:

public IActionResult Index(IssueModel searchCriteria)
{
    var bloods = from m in _context.Blood
                 select m;
    if (!string.IsNullOrEmpty(searchCriteria.SearchComponent))
    {
        //Blood Component
        bloods = bloods.Where(s => s.Component.Contains(searchCriteria.SearchComponent));
        //Blood Type : This is where I plan to search for a specific blood type.
    }
    return View(bloods);
}

As you can see, I'm happy to search the blood database for a certain component type. In the area I've marked I would like to search for blood that relates to a certain PlasType or RedBloodType.

Any ideas? Thanks!

Edit: Thanks to everyone who offered an answer. All the answers I've looked at have been incredibly useful not just in helping me crack this one, but improve my understanding of the topic.

The fact that your return statement ignores bloods is unhelpful... but moreover, you haven't really asked a question yet. What exactly are you stuck on? — Jon Skeet
– Jon Skeet, Commented Jan 22, 2016 at 13:48
You could continue your query. Given the blood.DonorId, you could find the Donor which matches your PlasmaType and RedBloodType criteria. Then, return the result of the query, not the original _context.Blood.List — Ian
– Ian, Commented Jan 22, 2016 at 13:53

Tauseef · Accepted Answer · 2016-01-22 14:03:41Z

1

i would just create simple sql query and then convert it to linq query.

Select distinct blood.* from blood
inner join donor on blood.donorid = donor.donorid
where donor.PlasType like 'param' or RedBloodType like 'param'

now convert this to a linq query

var filteredBlood = (from b in blood
                      join d in donor on b.DonorId equals d.DonorId
                      where d.PlasType.contains("param") || d.RedBloodType.contains("param")
                      select b).distinct().toList();

answered Jan 22, 2016 at 14:03

Tauseef

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Comments

smq93 · Accepted Answer · 2016-01-22 13:57:27Z

1

Don't you have the navigation property like Blood.Donors (if it's one to many relation)? You can access to it via this property but earlier you should include it:

Blood.Include(c => c.Donors);

answered Jan 22, 2016 at 13:57

smq93

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blogprogramisty.net · Accepted Answer · 2016-01-22 14:11:53Z

1

Like this:???

    result = new List<Blood>();

    foreach (var b in bloods)
    {
      if (_context.Donor.Where(d => d.id == b.BloodId)
                        .Any(d => (d.PlasType == "somethingsYouNow") || (d.RedBloodType == "somethingsYouNow"))
      {
        result.Add(b)
      }
    }


    return result;

edited Jan 22, 2016 at 14:11

answered Jan 22, 2016 at 13:55

blogprogramisty.net

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