Question

I use this predicate with EF and lamdba expression :

public class PredicateBuilder
{
    public static Expression<Func<T, bool>> True<T>() { return f => true; }
    public static Expression<Func<T, bool>> False<T>() { return f => false; }
}

public static class ExpressionExtensions
{
    public static Expression<Func<T, bool>> And<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
    {
        return first.Compose(second, Expression.And);
    }

    public static Expression<Func<T, bool>> Or<T>(this Expression<Func<T, bool>> first, Expression<Func<T, bool>> second)
    {
        return first.Compose(second, Expression.Or);
    }
}

Now I just want to dynamically build this query :

Query(ufe => (ufe.FilmEtat.filmetat_code == etatString && ufe.user_id == 2) || (ufe.FilmEtat.filmetat_code == etatString && ufe.user_id == 11)).ToList();

I already tried :

var predicate = PredicateBuilder.True<UtilisateurFilmEtat>();
int i = 0;
foreach (int utilisateurId in listUtilisateurId)
{
    if (i == 0)
        predicate = ufe => (ufe.FilmEtat.filmetat_code == etatString && ufe.user_id == utilisateurId);
    else
        predicate.Or(ufe => ufe.FilmEtat.filmetat_code == etatString && ufe.user_id == utilisateurId);

    i++;
}

The query is working but not return the good results…

I am becoming crazy 🙁

Need your help.

Thank you

Answer 1

Your question seems very similar to this one: Linq to SQL how to do "where [column] in (list of values)", although not an exact duplicate.

I can see that you’re trying to dynamically build a query by combining other querys with ||, which is what you’d want to do if you only had a comparison operator…

Instead, how about something like this: ufe => listUtilisateurId.Contains(ufe.user_id)