"cannot implicitly convert .." when using LINQ Where

Question

I'm trying to write a query in a c# program that gets all items out of a database where a particular id in that item is contained in a list I have. I also need to join on a few tables..

What I have is:

var data = from a in db.Apples.Where(a => myApples.contains(a.type))
           from b in db.Banans where b.Id = a.bananaPair.Id
           from c in db.Coconuts where c.Id = c.coconutPair.Id
           select new {
               apple = a,
               bananaName = b.name,
               coconutName = c.name,
           });

I get an error on "where b.Id = a.bananaPair.Id" that "cannot implicitly convert int to bool". I think I am mixing types.. the first where is a comparison, and the others is a join condition. How can I do both in the query? I need pieces of information from all 3 tables in my select object.

Thanks

== is equality = is assignment

tbddeveloper
– tbddeveloper

2014-07-31 18:45:53 +00:00
Commented Jul 31, 2014 at 18:45 — tbddeveloper
– tbddeveloper, Commented Jul 31, 2014 at 18:45

Matthew Haugen · Accepted Answer · 2014-07-31 18:46:16Z

2

Change it to

var data = from a in db.Apples.Where(a => myApples.contains(a.type))
       from b in db.Banans where b.Id == a.bananaPair.Id
       from c in db.Coconuts where c.Id == c.coconutPair.Id
       select new {
           apple = a,
           bananaName = b.name,
           coconutName = c.name,
       });

You had b.Id = a.bananaPair.Id. That assigns a.bananaPair.Id to b.Id. The reason your error was calling this assignment an int is because assignments return the value assigned. You want b.Id == a.bananaPair.Id, which tests whether they're equal.

As commenter @misterManager suggests, you could also use join here. Let me know if this doesn't work, though, it's been so long since I've used query syntax.

var data = from a in db.Apples.Where(a => myApples.contains(a.type))
       join b in db.Bananas on a.bananaPair.Id equals b.Id
       join c in db.Coconuts on c.coconutPair.Id equals c.Id
       select new {
           apple = a,
           bananaName = b.name,
           coconutName = c.name,
       });

By the way, I couldn't help but notice your c line: from c in db.Coconuts where c.Id == c.coconutPair.Id, should that be a.coconutPair.Id?

answered Jul 31, 2014 at 18:46

Matthew Haugen

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3 Comments

misterManager Over a year ago

its also worth mentioning that you can use join keyword as well.... ie: join b in db.Bananas on a.bananaPair.Id equals b.Id.... additionally let b = a.Bananas if the db has proper integrity and allows such a navigation option

jcam77 Over a year ago

Oh my goodness are you kidding me haha. That is embarrassing! How come with SQL in server management studio or other times double equals isn't necessary? Either way - big thank you!

misterManager Over a year ago

@jcam77 difference between sql and c# as languages. Your C# gets converted INTO sql which is what makes EF and other such frameworks so powerful. They don't execute C# necessarily... they actually transform your C# into SQL which is executed by the server and returned to you in a nice pretty object :) The sql that is output by your C# would NOT have the ==

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