Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IList'

Question

I have method :

        public DzieckoAndOpiekunCollection GetChildAndOpiekunByFirstnameLastname(string firstname, string lastname)
    {
        DataTransfer.ChargeInSchoolEntities db = new DataTransfer.ChargeInSchoolEntities();
        DzieckoAndOpiekunCollection result = new DzieckoAndOpiekunCollection();
        if (firstname == null && lastname != null)
        {
            IList<DzieckoAndOpiekun> resultV = from p in db.Dziecko
                          where lastname == p.Nazwisko
                          **select** new DzieckoAndOpiekun(
                         p.Imie,
                         p.Nazwisko,
                         p.Opiekun.Imie,
                         p.Opiekun.Nazwisko)
                      ;
            result.AddRange(resultV);
        }
        return result;
    }

and error in selected place :

Error 1 Cannot implicitly convert type 'System.Linq.IQueryable' to 'System.Collections.Generic.IList'. An explicit conversion exists (are you missing a cast?)

Any idea how solve my problem ? :/

Answer 1

Try this -->

 new DzieckoAndOpiekun(
                         p.Imie,
                         p.Nazwisko,
                         p.Opiekun.Imie,
                         p.Opiekun.Nazwisko).ToList()

Answer 2

You can use the .ToList() method to convert the IQueryable result returned to an IList, as shown below, after the linq query.

   public DzieckoAndOpiekunCollection GetChildAndOpiekunByFirstnameLastname(string firstname, string lastname)
{
    DataTransfer.ChargeInSchoolEntities db = new DataTransfer.ChargeInSchoolEntities();
    DzieckoAndOpiekunCollection result = new DzieckoAndOpiekunCollection();
    if (firstname == null && lastname != null)
    {
        IList<DzieckoAndOpiekun> resultV = from p in db.Dziecko
                      where lastname == p.Nazwisko
                      **select** new DzieckoAndOpiekun(
                     p.Imie,
                     p.Nazwisko,
                     p.Opiekun.Imie,
                     p.Opiekun.Nazwisko).ToList()
                  ;
        result.AddRange(resultV);
    }
    return result;
}

Answer 3

To convert IQuerable or IEnumerable to a list, you can do one of the following:

IQueryable<object> q = ...;
List<object> l = q.ToList();

or:

IQueryable<object> q = ...;
List<object> l = new List<object>(q);

Answer 4

You can replace IList<DzieckoAndOpiekun> resultV with var resultV.