I have a LINQ query, and I want to pass Person parameters to it. Probably it should be something like this.
Expression<Func<Person, long>> exp1 = person.CarId;
Expression<Func<Person, long>> exp2 = person.PetId;
var result = db.people.Select(x => new {PersonName = x.Name, EntityId = exp1}).ToList()
How can I do it?
I've used IQueryble to reuse parts of queries. It was something like the following:
var withPets = Get(GetWithPetId);
List<WithEntityId> Get(Func<IQueryable<Person>, IQueryable<WithEntityId>> transformer)
{
transformer(db.People.Where(...))
.Where( x => x.EntityId > 100)
.ToList();
}
IQueryable<WithEntityId> GetWithPetId(IQueryable<Person> people)
=> people.Select(x => new WithEntityId(x.Name, x.PetId));
IQueryable<WithEntityId> GetWithCard(IQueryable<Person> people)
=> people.Select(x => new WithEntityId(x.Name, x.CarId));
Vanilla EF do not allow such queries. I would suggest to use LINQKit. It needs just configuring DbContextOptions:
builder
.UseSqlServer(connectionString)
.WithExpressionExpanding(); // enabling LINQKit extension
Then you can use your expressions in the following way:
var result = db.people
.Select(x => new {PersonName = x.Name, EntityId = exp1.Invoke(x)})
.ToList()