ThreadPool问题

using System;
using System.Threading;

public class SimplePool
{
public static void Main(string[] args)
{
for (int i = 0; i < 100; i++)
ThreadPool.QueueUserWorkItem(new WaitCallback(t1), i.ToString());
//ThreadPool.QueueUserWorkItem(new WaitCallback(t2));
//为什么这一句会有错误：“t2”的重载均与委托“System.Threading.WaitCallback”不匹配？
Console.ReadKey();
}
static public void t1(object name)
{
Random rnd = new Random();
Thread.CurrentThread.Name = (string)name;
while (true)
{
Console.Write(Thread.CurrentThread.Name + " ");
Thread.Sleep(rnd.Next(5000));
}
}
static public void t2()
{
Random rnd = new Random();
Thread.CurrentThread.Name = rnd.Next(1000).ToString();
while (true)
{