Linq query for nested list in C#

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Hi guys,

I have a List<candidate>.

in this list, For each candidate, i have List<candidatecertificates>.

I have a dropdownlist of Certificates.

C#

I want to compare <candidatecertificate>.ceritifcateID
  with ddlCerifiticate_Selected_value.

I want to fetch all the candidates with particualr certificate ID, only.

What I have tried:

C#

private List<CandidateInfo> Candidates
{
            get
            {
                var _candidates = CandidateController.Instance.All.FindAll(item => item.Center.ID == ExamSession.Center.ID);
                foreach(var c in _candidates)
                {
                    foreach (var ct in c.CandidateCertificates)
                    {
                        var ct1 = ct.CertificationID == long.Parse(ddlCertificate.SelectedValue);
                        break;
                    }
                    return c;
                }
                return null;
            }
        }

i would like to write LINQ query for this.

can anyone plz help me.

Thanks

Posted 19-Oct-16 22:56pm

abdul subhan mohammed

Updated 20-Oct-16 2:32am

v2

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Comments

F-ES Sitecore 20-Oct-16 5:00am

Your code as posted makes no logical sense so it will be hard to convert to linq. If your logic isn't working now, converting it to linq isn't going to make it work by magic. This is what you have now as LINQ

var candidate = CandidateController.Instance.All.FindAll(item => item.Center.ID == ExamSession.Center.ID).FirstOrDefault();

abdul subhan mohammed 20-Oct-16 5:48am

that's why, i need help to make the query sensible.

johannesnestler 20-Oct-16 6:08am

does your Code work now? why change it? - just don't re-parse the selected value all the time during the loop (do it once outside)

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Nathan Minier · Accepted Answer · 2016-10-20T02:32:00

Just change the conditions that you are querying on. I'm converting your FindAll to a Where clause as I know that works for nested queries.

I'm also converting this to a method, since as a property the possibility exists that ddlCertificate has a null value, which will cause an exception if the property is called prematurely. Just call your parse on the selectedValue before passing it to the method.

C#

private List<CandidateInfo> Candidates(long selected)
{ 
   return CandidateController.Instance.All
      .Where(item => 
         item.Center.ID == ExamSession.Center.ID &&
         item.CandidateCertificates.Any(cert => cert.CertificationID == selected))
      .ToList();           
}

The key here is that (assuming you're running off a sensible ORM) this will be pushed down the pipe as a single query, returned as a single result, and not looped over by the application, sparing some cycles