C# List<T>.Add not adding properly
c#
Solution
private List<Note> _Notes;
public List<Note> Notes
{
get
{
return _Notes ?? new List<Note>();
}
set
{
_Notes = value;
}
}
The `get` is wrong. It should be:
get
{
if (_Notes == null) {
_Notes = new List<Note>();
}
return _Notes;
}
because otherwise you don't save the `new List<Note>()` you created and every time you use the `get` you recreate it (the `get` returns a `new List<Note>()` but doesn't modify `_Notes`, so every `get` checks `_Notes`, see it's `null` and return a `new List<Note>()`)
Note that if you hate the world (and your fellow programmers) you can compact the `get` to:
return _Notes ?? (_Notes = new List<Note>());
(see Ternary/null coalescing operator and assignment expression on the right-hand side?) I don't hate enough the world (and my fellow programmers) to do it :-)
Problem
Using `.Add` to add an instance of a class to a generic list is not working. To illustrate the problem, here are two simple example classes: ``` public class WorkOrder { private List<Note> _Notes; public List<Note> Notes { get { return _Notes ?? new List<Note>(); } set { _Notes = value; } } } public class Note { public string NoteText { get; set; } public System.DateTime Time { get; set; } public string User { get; set; } } ``` You may notice the coding in `get` on the `WorkOrder.Notes` property. I put this in so the property wouldn't be initialized with a null value (ref an answer to another question I posted on SO here). To utilize these classes: ``` public void Test() { WorkOrder tempWorkOrder = new WorkOrder(); Note tempNote = new Note() { User = "Aaron", Time = DateTime.Now, NoteText = "Work Order pulled from CSV Excel report." }; tempWorkOrder.Notes.Add(tempNote); } ``` I would expect the last line in `Test()` to add `tempNote` to the list of `Note` in `tempWorkOrder`. However, `tempWorkOrder.Notes` is null after this line completes. No errors or exceptions are thrown. I'm using VS2013 Express. What am I doing wrong?