哪位大神帮忙看看这个窗体程序哪里错了

using System;using System.Collections.Generic;using System.Data;using System.Drawing;using System.Linq;using System.Text;using System.Windows.Forms;namespace WindowsFormsApplication4{    public partial class Form1 : Form    {        public Form1()        {            InitializeComponent();        }        private void textBox2_TextChanged(object sender, EventArgs e)        {        }        private void button1_Click(object sender, EventArgs e)        {            int a, b, c,j,i=0;            a = int.Parse(textBox1.Text);            b = int.Parse(textBox2.Text);            for (c = a; c <= b;c++);            {                if (c % 3 == 0 && c % 5 == 0 && c % 100 != 0);                textBox3 .Text =textBox3 .Text +c.ToString()+'\t';                    i++;                    if (i % 5 == 0) ;                    {                        textBox3 .Text +="\r\n";                    }                }            }        }    }