linq连接3个表或条件

Question

I need to create a statement in LINQ with 3 tables and OR condition.

My function receives an integer, lets call it intZ . I have 3 tables: tableA , tableB and tableC .

tableA has columns int1 , int2 and intB . intB is related to tableB .

problem: int1 or int2 of tableA can be intZ and it has to match with one tableC record.

I need an OR condition, but I have no idea where to place it. Does it go in the where clause? Or in the equals clause?

At the moment, I know how to join 3 tables, but the condition is killing me.

What is the difference between the two ways to create statements in linq? Is there a performance impact?

edit: Okay, now I think it's more clear. intZ has to be related with intC from tableC , and this number can be int1 or int2 of tableA .

Answer 1

Just add it to a Where . In Linq2Sql this will be translated to an inner join (with or) on tableB

from a in tableA
from b in tableB.Where(x => x.A == a.A || x.B == a.B)
select new { a, b };

Answer 2

You can't use an "or" condition in joins in LINQ, as it only supports equijoins. But you should be able to do it in a where clause with no problems. For example:

var query = from rowC in tableC
            where rowC.intC == intZ
            from rowA in tableA
            where rowA.int1 == rowC.intC || rowA.int2 == rowC.intC
            join rowB in tableB on rowA.intB equals rowB.intB
            select new { rowA, rowB, rowC };

Answer 3

This may be helpful.

var locations = from r1 in 
          (from a in context.A
          join b in context.B
          on a.ID equals b.ID
          select new
          {
            a.Prop1,
            a.Prop2,
            b.Prop3,
            b.ID
          })
          join c in context.C
          on r1.ID equals c.ID
          select new
          {
            r1.Prop1,
            r2.Prop2,
            r2.Prop3,
            c.Prop4
          };

Answer 4

For the life of me, I couldn't get the .Where to work in my query (perhaps it's how I'm using LinqPad) but I was able to get the following to work:

from s in Stores
join a in Areas on s.AreaID equals a.ROWID
join r in Regions on a.RegionID equals r.ROWID
join e in Employees on 1 equals 1     // <-- produces a cartesian product
join t in Titles on e.TitleID equals t.ROWID
where e.AreaID == a.ROWID || e.RegionID == r.ROWID // <--filters the data based on OR stmt
where s.StoreNum == 469
select new { r.RegionName, a.AreaName, s.StoreNum, s.StoreName, t.JobCode, e.FirstName, e.LastName }

Answer 5

尝试这个：-

var result= tableA.SelectMany(a => tableB.Where(x => x.A == a.A || x.B == a.B), (a, b) => new {a, b});