C# uses preorder traversal, middle traversal and postorder traversal to print binary trees

public class BinaryTreeNode
{
 public BinaryTreeNode Left { get; set; }
 public BinaryTreeNode Right { get; set; }
 public int Data { get; set; }
 public BinaryTreeNode(int data)
 {
   = data;
 }
}
public enum TreeTraversal
{
  PREORDER,
  INORDER,
  POSTORDER
}
public void PrintTree(BinaryTreeNode root, TreeTraversal treeTraversal)
{
  Action<int> printValue = delegate(int v)
  {
   (v + " ");
  };
  switch (treeTraversal)
  {
   case :
    PreOrderTraversal(printValue, root);
    break;
   case :
    InOrderTraversal(printValue, root);
    break;
   case :
    PostOrderTraversal(printValue, root);
    break;
   default: break;
  }
}
public void PreOrderTraversal(Action<int> action, BinaryTreeNode root)
{
  if (root == null)
   return;
  action();
  PreOrderTraversal(action, );
  PreOrderTraversal(action, );
}
public void InOrderTraversal(Action<int> action, BinaryTreeNode root)
{
  if (root == null)
   return;
  InOrderTraversal(action, );
  action();
  InOrderTraversal(action, );
}
public void PostOrderTraversal(Action<int> action, BinaryTreeNode root)
{
  if (root == null)
   return;
  PostOrderTraversal(action, );
  PostOrderTraversal(action, );
  action();
}