The type arguments for method 'System.Linq.Queryable.SelectMany System.Linq.IQueryable

Question

While editing my Repository class an Error pops out

 var applicantList = (from a in context.Profiles
                             join app in context.APPLICANTs
                                on a.PROFILE_ID equals app.Profile_id into joined
                              from j in joined.DefaultIfEmpty()//.OrderBy(v => v.APPLICANT_ID)
                             select j //<--  this is APPLICANTs type
                               ).Take(1000);

   applicantdata = applicantList
                  .SelectMany(c => c.APPLICANTs) //this line added
                  .AsQueryable().OrderBy(v => v.APPLICANT_ID).ToList();

                if (applicantdata.Any())
                {
                    Cache.Set("applicants", applicantdata, 30);
                }
            }
            return applicantdata;

Im having an exception at

.SelectMany(c => c.APPLICANTs) //this line added

saying that :

The type arguments for method 'System.Linq.Queryable.SelectMany(System.Linq.IQueryable, System.Linq.Expressions.Expression>>)' cannot be inferred from the usage. Try specifying the type arguments explicitly

What EXACTLY are you trying to do? http://msdn.microsoft.com/en-us/library/system.linq.queryable.selectmany.aspx — Tom Chantler, May 20 '13 at 07:08
Im trying to do a Left join sir. .i red some questions here and tried to apply — Enrique Gil, May 20 '13 at 07:10
What is the type of `c.APPLICANTs` in your lambda `c => c.APPLICANTs`? Is it `IEnumerable` in a uniqye way? — Jeppe Stig Nielsen, May 20 '13 at 07:14
by the way: if u use a list `.OrderBy(v => v.APPLICANT_ID).ToList();` u can use `applicantdata.Count` instead of `if (applicantdata.Any())` — Roar, May 20 '13 at 07:22
You already asked this question: http://stackoverflow.com/questions/16641893/returning-null-values-while-trying-to-use-left-join — Dimitar Dimitrov, May 20 '13 at 07:26

score 4 · Accepted Answer · edited May 23 '17 at 10:25

4

SelectMany accepts a collection of object which each of them have a collection property inside.

You selected APPLICANTs collection at the first statement and running a SelectMany on it doesn't seem to be meaningful.

Checkout these links to understand the SelectMany better.

http://msdn.microsoft.com/en-us/library/bb534336.aspx
Difference Between Select and SelectMany

edited May 23 '17 at 10:25

Community

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1

answered May 20 '13 at 07:08

Jahan Zinedine

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do you have any suggestion on how i implement leftjoin – Enrique Gil May 20 '13 at 07:13
1

are you after the joined tables, or just the FKed table? – Christopher Stevenson May 20 '13 at 07:17

score 1 · Answer 2 · answered May 20 '13 at 07:13

1

SelectMany is used for 'flattening' a list of lists. You don't have a list of lists here. You have a list of anonymous joined rows.

It's a bit difficult to infer what you're querying for, but if you're looking to get the related rows (the APPLICANTs rows), you can use this:

var applicantList = (from a in context.Profiles
                     join app in context.APPLICANTs
                     on a.PROFILE_ID equals app.Profile_id
                     select app).Take(1000)

answered May 20 '13 at 07:13

Christopher Stevenson

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what am i trying to do is like this http://stackoverflow.com/questions/4497086/linq-left-join-and-right-join – Enrique Gil May 20 '13 at 07:19
`var applicantList = (from a in context.Profiles join app in context.APPLICANTs.DefaultIfEmpty() on a.PROFILE_ID equals app.Profile_id select new { prop1 = a.column1, prop2 = app.column1 }).Take(1000);` – Christopher Stevenson May 20 '13 at 07:22
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Here's a more detailed reference: http://codingsense.wordpress.com/2009/03/08/left-join-right-join-using-linq/ – Christopher Stevenson May 20 '13 at 07:23
The important parts are the `.DefaultIfEmpty()` on the joined table, which is how you make this a left join (instead of a join), and the `select new { ... }` which will make an anonymous class with the specified properties. You could just as easily declare a class to hold the data, and use `select new MyClassName { ... }`. – Christopher Stevenson May 20 '13 at 07:27
sir i will declare my Applicant and Profile class so can help me more – Enrique Gil May 20 '13 at 07:56

The type arguments for method 'System.Linq.Queryable.SelectMany System.Linq.IQueryable

2 Answers2