Question

I’d like to use the .Join() method in LINQ to perform the following SQL:

select * from Enquiries e, QuoteLines q where e.EnquiryId = q.EnquiryId and e.AccountNum = '123' and q.LineNumber = 'ABC123'

The parameters used for AccountNum and LineNumber will be dynamically passed to the method.

How would I transfer this to use the LINQ .Join() method?

public ActionResult EnquirySearch(string id)
{
    var enquiries = new List<Enquiries>();    

    if(id.Contains(' '))
    {
        string[] searchArr = id.Split(' ');
        // want to do my LINQ here
        // this will be split so the first element in the array is the AccountNum
        // and the second element in the array is the LineNumber
    }
    else
    {
        enquiries = context.Enquiries.Where(x=>x.QuoteRef.Contains(id) 
        || x.AccountNum.Contains(id) || x.Owner.Contains(id));
    }
    return View(enquiries);
}

Answer 1

It’s easier to express a join in an expression query, where it would be something like:

var query = from e in Enquiries
            join q in QuoteLines on e.EnquiryId equals q.EnquiryId
            where e.AccountNum == accountNum && q.LineNumber == lineNumber
            select new { Enquiry = e, QuoteLine = q };

Or you could filter “early” – which would make a difference in LINQ to Objects, but almost certainly not in LINQ to SQL / EF:

var query = from e in Enquiries
            where e.AccountNum == accountNum
            join q in QuoteLines.Where(qq => qq.LineNumber == lineNumber)
              on e.EnquiryId equals q.EnquiryId
            select new { Enquiry = e, QuoteLine = q };