Is there a c# language construct that will allow me to add items to a readonly collection property in a constructor? I want to do something like this:
public cl
You can add a backing field to the "Children" property, then just populate the backing field during construction.
Like so
public class Node
{
private IList<Node> _Children;
public IList<Node> Children { get { return _Children; } }
public Node(IList<Node> children)
{
_Children = children;
}
}
Then you can do this
var node = new Node((new ObservableList<Node>()).Add(new Node()));
If you have a property of type List that is get
only, that only means you can't set that property, you can still add things to the list.
You could however expose an IEnumerable
property instead and have a constructor that takes a list(or another IEnumerable
more likely).
Property initializers do not work since the compiler will just rewrite them to regular property assignments.
I'd do this:
public class Node{
public IEnumerable<Node> Children {get; private set;}
public Node(IEnumerable<Node> children){
Children = children.ToList();
}
}
if you can't change the Node
class, I suggest writing a helper class similar to this:
public static Node Create(IEnumerable<Node> children)
{
var n = new Node();
foreach (var c in children)
n.Children.Add(c);
return n;
}
To use the collection initializer syntax from you second code snippet your Node class must implement IEnumerable and have a public method with the signature
void Add(Node child)
Hence such a class cannot offer the immutability you desire. I think the best solution to your problem would be to do this
public class Node
{
public readonly IEnumerable<Node> Children;
public Node(IEnumerable<Node> children)
{
Children = children;
}
}
or if you do not like the deferred execution of IEnumerable:
public class Node
{
public readonly ReadOnlyCollection<Node> Children;
public Node(IEnumerable<Node> children)
{
Children = new ReadOnlyCollection<Node>(children);
}
}
Try this. It is definitely possible to add elements on construction
var node = new Node
{
Children =
{
new Node(),
new Node()
}
};