如何使字符串为空以转换为C＃中的文本框

问题描述

Here is the form i made

当我在文本框中输入一个空值时，我遇到了未处理的异常页面。当用户在文本框中输入空值时，我想显示一个错误消息框，我该怎么办？

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

        Random rnd = new Random();
        int number;
        int answer;
        private void button1_Click(object sender,EventArgs e)
        {
            

            
            number = rnd.Next(1,101);

            label1.Text = number.ToString();

            
        }

        private void button2_Click(object sender,EventArgs e)
        {
            answer = Convert.ToInt32(textBox1.Text);

            if(answer == number)
            {
                MessageBox.Show("Welcome to the page","Welcome!",MessageBoxButtons.OK,MessageBoxIcon.information);
            }
            else if(String.IsNullOrEmpty(textBox1.Text))
            {
                MessageBox.Show("Icorrect entrance","You can not acces to the page",MessageBoxIcon.Error);
            }
            else
            {
                MessageBox.Show("Icorrect entrance",MessageBoxIcon.Error);
            }
        }
    }

解决方法

只需在方法的开头添加空测试：

int.TryParse()

您也可以使用Convert代替TextChanged来更好地捕获转换错误：。

How the int.TryParse actually works

您也可以简单地将按钮默认设置为禁用，并在private void textBox1_TextChanged(object sender,EventArgs e) { button.Enable = textBox1.Text != ""; } 事件上添加此处理程序：

int.TryParse

也可以在这里也private void textBox1_TextChanged(object sender,EventArgs e) { button.Enable = textBox1.Text != "" && int.TryParse(textBox1.Text,out _); } ：

private void button2_Click(object sender,EventArgs e)
{
  answer = Convert.ToInt32(textBox1.Text);
  if ( answer == number )
    MessageBox.Show("Welcome to the page","Welcome!",MessageBoxButtons.OK,MessageBoxIcon.Information);
  else
    MessageBox.Show("Icorrect entrance","You can not acces to the page",MessageBoxIcon.Error);
}

因此，仅当按钮不为空且不可转换且用户体验一致时才启用按钮。

现在按钮单击处理程序为：

import speech_recognition as sr

r = sr.Recognizer()
m = sr.Microphone()

try:
    print("A moment of silence,please...")
    with m as source: r.adjust_for_ambient_noise(source)
    print("Set minimum energy threshold to {}".format(r.energy_threshold))
    while True:
        print("Say something!")
        with m as source: audio = r.listen(source)
        print("Got it! Now to recognize it...")
        try:
            value = r.recognize_google(audio)

            if str is bytes:
                print(u"You said {}".format(value).encode("utf-8"))
            else:
                print("You said {}".format(value))
        except sr.UnknownValueError:
            print("Oops! Didn't catch that")
        except sr.RequestError as e:
            print("Uh oh! Couldn't request results from Google Speech Recognition service; {0}".format(e))
except KeyboardInterrupt:
    pass