Question

I’m trying to display a list coming from my database using Linqtosql but I guess I’m making it wrong.

I wrote the SPROC to retrieve the data here if you want further info:
And this is my code:

     protected List<MySubject> GetSubjects(int userID, string Datetime)
    {
        userID = user_id;
        string[] dates = Datetime.Split('-');
        int year = int.Parse(dates[2]);
        int month = int.Parse(dates[1]);
        int day = int.Parse(dates[0]);
        ClassDAO classClass = new ClassDAO();
        List<MySubject> myTodaySubjects = GetSubjectsLinq(userID, day);
        GetSubjectsLinq(userID, day);
        return myTodaySubjects;
    }

    private List<MySubject> GetSubjectsLinq(int UserId, int day)
    {
        MySchoolDBDataContext db = new MySchoolDBDataContext();
        string Suserid = UserId.ToString();
        string Sday = day.ToString();
        var sub = db.GetSubjects(Sday , Suserid);
        return sub.ToList<MySubject>();
     }

This Line "return sub.ToList<MySubject>();" shows this error :

Error   21  Instance argument: cannot convert from 
'System.Data.Linq.ISingleResult' to 'System.Collections.Generic.IEnumerable'. 

Do you know how can I fix it ?

Answer 1

Check your

db.GetSubjects (Sday , Suserid);

method(stored procedure). It looks like it is returning only one single value of a certain type, which means that it cannot be assigned to an IEnumerable<T> such as a List<T>.

Since you use a stored procedure in LINQ, it’ll generate a class T(procedure name + “Result”) for you automatically to store the data. The returned type is always ISingleResult<T>.

So, you can try the following:

ISinlgeResult<MySubjectResult> sub = db.GetSubjects(Sday , Suserid);
foreach(MySubjectResult val in sub)
{
...
}

or just use db.GetSubjects (Sday , Suserid).ReturnValue;