使用 2 个表实现 ASP.NET MVC5 搜索功能

Question

I have created two tables: Claim and ClaimAttachments. I'm trying to join them on ClaimID in order to get the filtered data from both the tables.

public ActionResult Index(int? search) {

        if (search!=null)
        {
            var Product = (from P in db.Claims
                           join C in db.ClaimAttachments on
                           P.ClaimID equals C.ClaimID

                           select new Claim
                           {
                               ClaimID = P.ClaimID,
                               ClaimBatchID = P.ClaimBatchID,
                               PatientControlNumber = P.PatientControlNumber,
                               PatientFirstName = P.PatientFirstName,
                               PatientLastName = P.PatientLastName,
                               ServiceFromDate = P.ServiceFromDate,
                               ServiceToDate = P.ServiceToDate,
                           });
             return View(db.Claims.Where(x => x.ClaimID == search).ToList());
           

        }
        
        else
        {
            return View(db.Claims.ToList());
        }

I'm able to get the searched result but from single table. The join is not working.

Answer 1

Currently you're only selecting from the Claims data:

return View(db.Claims.Where(x => x.ClaimID == search).ToList());

You have a join query just above that line of code:

var Product = (from P in db.Claims
               join C in db.ClaimAttachments on
               P.ClaimID equals C.ClaimID

               select new Claim
               {
                   ClaimID = P.ClaimID,
                   ClaimBatchID = P.ClaimBatchID,
                   PatientControlNumber = P.PatientControlNumber,
                   PatientFirstName = P.PatientFirstName,
                   PatientLastName = P.PatientLastName,
                   ServiceFromDate = P.ServiceFromDate,
                   ServiceToDate = P.ServiceToDate
               });

But you don't do anything with the results of that query. It sounds like you meant to use the results of that query (which is in the Product variable, which incidentally should probably have a plural name since it's a collection) instead of just selecting from db.Claims . Something like this:

return View(Product.Where(x => x.ClaimID == search).ToList());

Note however that you're still only selecting data from one table. Though the join operation may alter the results of that selection. But the selection itself is here:

select new Claim
{
    ClaimID = P.ClaimID,
    ClaimBatchID = P.ClaimBatchID,
    PatientControlNumber = P.PatientControlNumber,
    PatientFirstName = P.PatientFirstName,
    PatientLastName = P.PatientLastName,
    ServiceFromDate = P.ServiceFromDate,
    ServiceToDate = P.ServiceToDate
}

Notice how every value selected is from the P alias, which is defined here:

from P in db.Claims

So you're successfully joining the two tables, but only selecting data from one of the two tables. If you want to also select data from the other table then, well, you need to select data from the other table. For example, if there's a property on that table called SomeProperty that you want to select then you'd need to select it, and into an object which has that property.

For example, you might create a view model (let's call it ClaimViewModel as an example) which represents a combined record of the two tables, containing the properties you want from each. Then you'd select into that type:

select new ClaimViewModel
{
    ClaimID = P.ClaimID,
    ClaimBatchID = P.ClaimBatchID,
    PatientControlNumber = P.PatientControlNumber,
    PatientFirstName = P.PatientFirstName,
    PatientLastName = P.PatientLastName,
    ServiceFromDate = P.ServiceFromDate,
    ServiceToDate = P.ServiceToDate,
    SomeProperty = C.SomeProperty // <--- here
}

This would select the combined data into a list of ClaimViewModel objects, which you'd then filter based on your "search" and return to your view just like you do with the Claims objects now. And of course that view would need to be updated to expect a collection of ClaimViewModel objects instead of a collection of Claim objects.