Question

I’m creating a list of class “Task” in a way such as this.

List<Task> toDoList = new List<Task>;

Task is a base class and have designed it as such:

 public class Task : IDetail
{
    string _taskName;            //Task title.
    string _taskDescription;     //Task description.

    public Task(string tn, string td) //Constructor.
    {
        _taskName = tn;
        _taskDescription = td;
    }

    // Method set or return _taskName.
    public string taskName
    {
        get
        {
            return _taskName;
        }

        set
        {
            _taskName = value;
        }
    }

    //Method to set or return _taskDescription.
    public string taskDescription
    {
        get
        {
            return _taskDescription;
        }

        set
        {
            _taskDescription = value;
        }
    }

    public virtual void editList()
    {
        Creator editCreator = new Creator();
        editCreator.Show();
    }


}

What i’ve been trying todo is call methods that exists within the inherited class like one the one i have designate “Note” and have defined it as follows.

class Note : Task, IDetail
{
    string _noteDescription;

    public Note(string nd, string tn, string td)    //Constructor.
        : base(tn, td)
    {
        _noteDescription = nd;
    }

    //Method to set or return _noteDescription.
    public string noteDescription
    {
        get
        {
            return _noteDescription;
        }

        set
        {
            _noteDescription = value;
        }
    }

    public override void editList()
    {
        noteBuilder editNote = new noteBuilder();
        editNote.Show();
    }
}

However when i try to call a method of the inherited task on the list i get an error. I am trying to access the method as such:

toDoList.ElementAt(x).noteDescription;

My question is how do i prevent an error from occurring?

the error states

‘toDoList.Task’ does not contain a definition for ‘noteDescription’ and no extension method etc etc.

Should i perhaps be declaring the base class as Abstract? or is there something else i am missing?

Many thanks in advance

Answer 1

You’ve got a List<Task>. That could contain any kind of Task reference – e.g. a different derived type, not a Note. Either you want a List<Note> (so it can all be type-safe), or you’ll need to cast the element of the list to Note:

Note note = (Note) toDoList[x];
string description = note.noteDescription;

(Given that you’ve got a List<T>, you don’t need to use ElementAt – use the indexer.)