Build dynamic LINQ?

Question

I\'m using LINQ to query data. Consider a case where the user only wants to report on say 1 of the 3 fields? (see below)

Can anyone tell me how to build the query d

Answer 1

You could do something like this:

var query = from cl in db.tblClaims
                        join cs in db.tblCases
                            on cl.ref_no equals cs.ref_no
                        where cl.claim_status == "Appeal"
                        select new
                        {
                            Ref = cs.ref_no,
                            ClaimType = cl.claim_type,
                            ClaimStatus = cl.claim_status,
                            AppealDate = cl.appeal_date,
                            cs.referred_from_lho,
                            cs.adviser
                        };

if(!string.IsNullOrEmpty(txtReferedFromDate.Text) 
   && !string.IsNullOrEmpty(txtReferedToDate.Text))
  query = query.Where(cl => 
                   cl.appeal_date >= Convert.ToDateTime(txtReferedFromDate.Text) 
                && cl.appeal_date <= Convert.ToDateTime(txtReferedToDate.Text));

if(!string.IsNullOrEmpty(dlLHO.Text))
  query = query.Where(cl => cl.referred_from_lho == dlLHO.Text);

if(!string.IsNullOrEmpty(dlAdviser.Text))
  query = query.Where(cl => cl.adviser == dlAdviser.Text);

gvReport.DataSource = 
      query.Select(o => new { o.Ref, o.ClaimType, o.ClaimStatus, o.AppealDate });

This would only use those fields as filters if they had values to filter on, otherwise they wouldn't be used in the query.