为什么在事件处理程序中无法识别变量？

Question

我对这段代码有两个问题.我遇到了麻烦,因为提交按钮事件无法识别在文本框事件中计算的变量,并且因为文本框事件未将我的if语句识别为语句.你可以在下面的评论中看到我遇到麻烦的地方.

 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;

 namespace WindowsFormsApplication11 
 {
public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
    }


    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void textBox1_TextChanged(object sender, EventArgs e)
    {
        int points;

        int userInput = int.Parse(textBox1.Text);

        if (userInput == 0)

        {
            points == 5; //I CANNOT COMPILE BECAUSE APPARENTLY I AM NOT ALLOWED TO USE
                         THIS AS A STATEMENT? 
        }

        if (userInput == 1)

        { 
            points == 10;
        }

        if (userInput == 2)

        {
            points == 20;
        } 

        if (userInput ==3)

        {
            points == 30;
        }

        else

        {
            points == 40;

        }

    }

    private void button1_Click(object sender, EventArgs e)
    {
        MessageBox.Show = ("You have been awarded" + textBox1.points + "points");
    } //I WANT TO BE ABLE TO RETRIEVE THE POINTS CALCULATED USING THE CALCULATION IN
      TEXT BOX, BUT I CANNOT COMPILE THE BUTTON EVENT DOES NOT RECOGNIZE THE POINTS
      VARIABLE



    private void label1_Click(object sender, EventArgs e)
    {

    }
 }
}

Answer 1

该==符号是一个比较符号不是赋值符号

你需要使用

if (userInput == 2) // this is a comparison
{ 
    points = 20; // this is an assignment
}