C#字符串判断

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication6
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
string str = textBox1.Text;
string newstr2 = ""; //用来保存过滤之后的串
int zimu = 0; int shuzi = 0; int qita = 0;
for (int i = 0; i < str.Length; i++)
{
if (str[i] >= '0' && str[i] <= '9')
{ //如果是数字，那么统计并放到新串中
shuzi++;
newstr2 += str[i];
}
else if (str[i] >= 'a' && str[i] <= 'z' || str[i] >= 'A' && str[i] <= 'Z')
{
zimu++;
}
else
{ //如果是其他，那么统计并放到新串中
newstr2 += str[i];
}
qita = str.Length - zimu - shuzi;
textBox2.Text = zimu.ToString();
textBox3.Text = shuzi.ToString();
textBox4.Text = qita.ToString();
}
string newstr="";
//反序
for (int i = str.Length - 1; i >= 0; i--)
{
newstr += str[i];
}
textBox6.Text = newstr;

//判断是否是回文
if (str == newstr)
{
textBox5.Text = "yes";
}
else
{
textBox5.Text = "no";
}
//输出过滤后的串
textBox7.Text = newstr2;
}
}
}