programmatic where in clause for PredicateBuilder

Question

I have extracted the relevant sections of the codebase to illustrate. Am really stuck on something potentially simple.

for information, in the database there is a one to many relationship between p and entity1.

predicate = PredicateBuilder.False<myType>();

.....

predicate = predicate.And(p => p.entity1.FirstOrDefault().id == 1 || p.entity1.FirstOrDefault().id == 2);

What I really need is to programmatically do the ( p.entity1.FirstOrDefault().id == 1 || p.entity1.FirstOrDefault().id == 2 )

forexample below

List<int> listOfId = new List<int>(){1,2,3,4,5,6,7,8,9};

predicate = predicate.And(p => p.entity1.id.wherein(listOfid);

Is there anyway this is possible please, it is quite critical to me.

Answer 1

Use Contains instead:

List<int> listOfId = new List<int>(){1,2,3,4,5,6,7,8,9};

predicate = predicate.And(p => listOfid.Contains(p.entity1.id));

Answer 2

In this particular case, the Contains method (as in @MarcinJuraszek's answer) is the way to go.

However, if you need to mix and match And s and Or s, you can do this:

predicate = PredicateBuilder.True<myType>();
//other clauses
.....
List<int> listOfId = new List<int>(){1,2,3,4,5,6,7,8,9};
var orClause = PredicateBuilder.True<MyType>();

foreach (var id in listOfId)
{
  orClause = orClause.Or(p => p.entity1.FirstOrDefault().id == id);
}

predicate = predicate.And(orClause);

(lifted from here )