下面C# Append()哪里错了？

Question

using System;

class List
{
Entry head;

class Entry
{
double data;
Entry next;

public Entry(double d)
{
data = d;
next = null;
}

public double Data
{
get { return data; }
set { data = value; }
}

public Entry Next
{
get { return next; }
set { next = value; }
}

public override string ToString()
{
return string.Format("{0:F2}", data);
}
}

public List()
{
head = null;
}

public void Append(double d)
{
Entry tmp = new Entry(d);
Entry current = head;
if (head == null)
{
head = tmp;
}
else
{
while (current != null)
{
current = current.Next;
}
current = tmp;
}
}

public override string ToString()
{
Entry current = head;
string result = "";

if (current == null)
{
result = "Empty List";
}
else
{
while (current != null)
{
result += string.Format("{0} ", current.ToString());
current = current.Next;
}
}

return result;
}
}

class TestProgram
{
static void Main()
{
List l = new List();

Console.WriteLine("\nNewly Constructed List");
Console.WriteLine(l);

l.Append(5.0d);
l.Append(-12.4d);
l.Append(36.5d);
l.Append(7.0d);
l.Append(42.0d);
l.Append(12.0d);

Console.WriteLine("\nList After Append Operations");
Console.WriteLine(l);
}
}

要求编的只有Append那个方法所以错误应该出在那里
题目要求输出5.00 -12.4.。。。。那些数字，但是现在永远都只出现5.00后面的都没有
要怎么改才能输出所有的数？谢谢！

Answer 1

List l = new List();这儿有错误吧？放在VS2010里编译报错！List<T> item=new List<T>(); 只能用Add（）或Insert（）等方法！
StringBuilder sb=new StringBuilder() 然后才可以sb.Append("");

Answer 2

List l = new List();
这样的话你需要用一个foreach 或者是for循环输出才可以。他是一个集合不是一个对象

Answer 3

Append（）方法里面对Head的赋值只有一次，就是在Head==null的时候，所以你Head里的Data永远只有一个5.0

Answer 4

list集合，需要遍历，才能全部输出的。和数组一样需要遍历输出