I'm pretty new to Visual C#. I have a class called Node and a List of Nodes called children. The goal is to make a Node tree. Each Node except the root Node has exactly one parent. Each Node has 0 or more children. To that effect, as part of my Node class I have a data member called children:

List<Node> children;

I am trying to add a child Node to a Node, but I only want to add it to the List if it is not already in the List. Here is what I have. The function below is a member function of the Node class:

// children is of type List<Node>
public void AddChild(Node childNode)

Line 3 gives me an error. I am not using Exists right. The example code I have seen has you write a boolean function that you pass to the Exists function, but those functions all have certain criteria (i.e. age > 25). My situation does not involve needing to check the data members of any . I just want to add a Node to the List , but make sure that I have no duplicates.

Do I want to use Exists and if so, do I need to write a boolean function of some kind. Thanks.

List.Exists () Method requires the Predicate. That means write your own method to search whether the Node is already Exists.


private static bool MyPredicate (Node s)
//        Check Node is Existing
//            return true;
//        else
//            return false;


if ( !this.children.Exists (MyPredicate) )

O.K., thanks. That clears some stuff up. I'll give it a shot. I'm actually wondering now, though, whether Contains would be better than Exists for my particular situation?

if ( !this.children.Contains (childNode) )