How to write IQueryable Join using lambda?

Question

I have next table:

MyTable
(
ParentId Integer,
Type Integer,
ProdId String,
Date DateTime,
Status Integer
);

I want to query as next:

var res = from tout in myTable.Where(t1 => t1.Type == 1)
                join tin in myTable.Where(t2 => t2.Type != 1)
        on tout.ParentId equals tin.ParentId
                where tout.ProdId == tin.ProdId && tout.Status > tin.Status
                orderby tout.Date
                select new MyTableStructure
                {
            ...
        };

How to write same as IQueryable using lambda?

Please correct me if I'm wrong, but from researching (b/c I didn't know how to do it either), it seems that both syntax look identical. However, it's the type that you're assigning to that makes the difference. (ie - IQueryable<MyTableStructure> res = ..... vs IEnumerable<MyTableStructure> res = ...... dotnettricks.com/learn/linq/ienumerable-vs-iqueryable — Rob Scott
– Rob Scott, Commented Mar 14, 2017 at 10:43
I recommend whenever using Joins in LINQ queries to always use the standard method instead of lambda. Reason being is that the Join syntax gets a little confusing (at least for me), and is easier read using the standard way. stackoverflow.com/questions/2767709/… — Rob Scott
– Rob Scott, Commented Mar 14, 2017 at 12:35

Vecchiasignora · Accepted Answer · 2017-03-14 12:34:36Z

9

Something like this

var query1 = myTable.Where(t1 => t1.Type == 1);
var query2 = myTable.Where(t2 => t2.Type != 1);
var join = query1.Join(query2, x => x.ParentId, y => y.ParentId, (query1, query2) => new { query1 , query2 }).Where(o => o.query1.ProdId == o.qyuery2.prodId).......

your order by next and Something

answered Mar 14, 2017 at 12:34

Vecchiasignora

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1 Comment

Ksice Over a year ago

Thanks a lot! The only note (it takes me some time to realize what's exactly wrong) - new { query2 , query1 } - wise-versa order should be there, to match with original join

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