c＃類從泛型繼承，方法返回類型

Question

我有應該是一棵樹的通用類，我想繼承這樣的類：

public class Tree<T> {
    private HashSet<Tree<T>> leaves;
    private T data;

    public Tree() {
        leaves = new HashSet<Tree<T>>();
    }

    public Tree(T data) : this() {
        this.data = data;
    }

    public T Data {
        get {
            return this.data;
        }
        set {
            data = value;
        }
    }

    public virtual Tree<T> findInLeaves(T data) {
        foreach(Tree<T> leaf in leaves) {
            if(leaf.Data.Equals(data)) {
                return leaf;
            }
        }
        return null;
    }
}

public class ComboTree : Tree<IComboAction> {
    private ComboMovement movement;

    public ComboTree() : base() {
        Movement = null;
    }

    public ComboTree(IComboAction action) : base(action) {
        Movement = null;
    }

    public ComboMovement Movement {
        get {
            return this.movement;
        }
        set {
            movement = value;
        }
    }
}

放置數據效果很好，但是當我嘗試使用方法findInLeaves時，我總是得到null。 我知道類型轉換存在問題，但是為什么ComboTree繼承Tree？

void readMove(IComboAction action) {
    ComboTree leaf = (ComboTree)currentLeaf.findInLeaves(action);
}

問題是為什么以及如何解決？

編輯：我創建了控制台程序，運行它並且它可以工作。 因此，這肯定是我的引擎問題！

Answer 1

public ComboTree(IComboAction action)
    : base(action)
{
    Movement = null; // <---- You are nulling Movement in the second constructor
}