How to use where clause in linq?

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I am trying to pass the following query string "api/test?cvr=cvr&cvr=trd", but i keep getting an empty array of data.

if I search api/test?cvr=cvr, i get 10 results and if search api/test?cvr=trd, i get 1 result and when I search them together i get no data.

C#

public IEnumerable<database_data> GetType(string cvr)
       {
           DateTime yesterday = DateTime.Today.AddBusinessDays(-1);

           var data = from c in db.database_data
                      where c.UploadDate == yesterday
                      where (c.Cover == cvr ||
                       c.Cover == cvr)
                      select c;
           return data.ToList();
       }

I cannot seem to get this functionality to work. Any help would be very much appreciated.
Thank you

Posted 20-Jan-14 3:56am

miss786

Updated 20-Jan-14 4:30am

v2

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Marco Bertschi · Answer 1 · 2014-01-20T04:32:00

Solution 1

Have a look at this sample[^], taken from the MSDN page 101 LINQ Samples[^]

Edit: Are you sure that there are data entries from yesterday in your DB?

Posted 20-Jan-14 4:32am

Marco Bertschi

Updated 20-Jan-14 4:33am

v2

JoCodes · Answer 2 · 2014-01-20T04:33:00

Editing according to the Question Edit.

You Can try debugging the linq query by different ways to check if it returns rows.

One easy way is to debug by splitting the query to check

SQL

var data = from c in db.database_data
                       where c.UploadDate == yesterday
                       select c;
data =data.where (c.Cover == cvr || c.Cover == cvr)// for debugging purpose combine it to one once checking

Check whether the conditions are satisfied. Before that check that records are returned before applying filters.

Pete O'Hanlon · Answer 3 · 2014-01-20T04:50:00

Well, to combine clauses in a where statement, all you need to do is:

C#

var data = from c in db.database_data
                       where c.UploadDate == yesterday &&
                        c.Cover == cvr
                       select c;

However, you might find that you get an issue with testing against UploadDate. The value you are storing in yesterday includes the time portion, so if UploadDate is actually a date, use

C#

c.UploadDate.Date == yesterday.Date

in your test.

How to use where clause in linq?

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