How should I use properties when dealing with read-only List<T> members
c#, collections, readonly
Solution
You can expose it AsReadOnly. That is, return a read-only `IList<T>` wrapper. For example ...
public ReadOnlyCollection<int> List
{
get { return _lst.AsReadOnly(); }
}
Just returning an `IEnumerable<T>` is not sufficient. For example ...
void Main()
{
var el = new ExposeList();
var lst = el.ListEnumerator;
var oops = (IList<int>)lst;
oops.Add( 4 ); // mutates list
var rol = el.ReadOnly;
var oops2 = (IList<int>)rol;
oops2.Add( 5 ); // raises exception
}
class ExposeList
{
private List<int> _lst = new List<int>() { 1, 2, 3 };
public IEnumerable<int> ListEnumerator
{
get { return _lst; }
}
public ReadOnlyCollection<int> ReadOnly
{
get { return _lst.AsReadOnly(); }
}
}
Steve's answer also has a clever way to avoid the cast.
Problem
When I want to make a value type read-only outside of my class I do this: ``` public class myClassInt { private int m_i; public int i { get { return m_i; } } public myClassInt(int i) { m_i = i; } } ``` What can I do to make a `List<T>` type readonly (so they can't add/remove elements to/from it) outside of my class? Now I just declare it public: ``` public class myClassList { public List<int> li; public myClassList() { li = new List<int>(); li.Add(1); li.Add(2); li.Add(3); } } ```