Question

C#if else 规则

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

namespace lianxi2
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}

private void button1_Click(object sender, EventArgs e)
{
this.Close();
}

private void button2_Click(object sender, EventArgs e)
{
int lYSS = int.Parse(textBox1.Text);
int rYSS = int.Parse(textBox2.Text);
int dSu = 1;
string ySF = "";
if (jianFaYSF.Checked == true)
dSu = lYSS - rYSS;
else if (jiaFaYSF.Checked == true)
dSu = lYSS + rYSS;
textBox3.Text = dSu.ToString();
textBox4.Text = textBox1.Text+ySF +textBox2.Text +ySF +textBox3.Text ;
}

}
}
代码如上，我想判断在textBox4.Text显示的+或者-号这么写不成吗？〉可以添加天IF判断里就出错

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Answer 1

public static boolean isNumeric(String str){
for (int i = str.length();--i>=0;){
if (!Character.isDigit(str.charAt(i))){
return false;
}
}
return true;
}