BNode类：

namespace btree.Tree {
    public class BNode<T> {
        public T data;
        public BNode<T> left;
        public BNode<T> right;

        public BNode(T data, BNode<T> left=null, BNode<T> right=null) {
            this.data = data;
            this.left = left;
            this.right = right;
        }
    }
}

BTree类

using System;

namespace btree.Tree {
    public class BTree<T> {
        public BNode<T> root;

        public void preOrder() {
            Console.Write("先根遍历二叉树:");
            preOrder(this.root);
            Console.WriteLine();
        }
        public void preOrder(BNode<T> p) {
            if(p!=null) {
                Console.Write(p.data);
                preOrder(p.left);
                preOrder(p.right);
            }
        }

        public void inOrder() {
            Console.Write("中根遍历二叉树:");
            inOrder(this.root);
            Console.WriteLine();
        }

        public void inOrder(BNode<T> p) {
            if(p!=null) {
                inOrder(p.left);
                Console.Write(p.data);
                inOrder(p.right);
            }
        }

        public void postOrder() {
            Console.Write("后根遍历二叉树:");
            postOrder(this.root);
            Console.WriteLine();
        }

        public void postOrder(BNode<T> p) {
            if(p!=null) {
                postOrder(p.left);
                postOrder(p.right);
                Console.Write(p.data);
            }
        }
    }
}

测试程序：

using System;
using btree.Tree;

namespace btree
{
    class Program
    {
        static void make(ref BTree<char> bTree) {
            BNode<char> d_node = new BNode<char>('D',null,new BNode<char>('G'));
            BNode<char> b_node = new BNode<char>('B',d_node,null);
            BNode<char> f_node = new BNode<char>('F', new BNode<char>('H'), null);
            BNode<char> c_node = new BNode<char>('C', new BNode<char>('E'), f_node);
            BNode<char> a_node = new BNode<char>('A',b_node, c_node);
            bTree.root = a_node;
        }
        static void Main(string[] args)
        {
            BTree<char> tree = new BTree<char>();
            Program.make(ref tree);
            tree.preOrder();
            tree.inOrder();
            tree.postOrder();
        }
    }
}

输出结果：

1.png

原树结构：

2.png