好像很多错，我在我电脑里也是不出来。

呵呵

新手学习中......

textbox1.text=y.tostring();

using System;
using System.Collections.Generic;
using
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;

namespace WindowsApplication3
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
           int a,b,y;
            a=13;  b=14;
            y=Max (a,b);
            textBox1.Text = y.ToString();
        }

       private  int Max(int n1, int n2)
        {

            if (n1 > n2)
            {
                return n1;
            }
            else
            {
                return n2;

            }

        }



    }

}
正确的。