c# - 在带有按钮和文本框的表单中运行几个错误

Question

这是我的代码:

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 FJBch09ex10
{


    public partial class Form1 : Form
    {
        Random r = new Random();
        int num = r.Next(0, 100);
        int counter = 0;

        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void btn1_Click(object sender, EventArgs e)
        {
            counter++;

            if (int.Parse(txt1.Text) > num)
            {
                lbl1.Text = "the number is too high";
                Form1.BackColor = HotTrack;


            }
            else {
                lbl1.Text = "the number is too low";
                Form1.BackColor = MenuHighlight;
            }

        }


    }
}

目前r.Next中的r运行出错。 Form1.BackColor 尝试也都是运行错误。知道为什么这些运行错误吗？ r 表示“字段初始值设定项不能引用非静态字段...”Form1 表示“非静态字段需要对象引用...”

Answer 1

public partial class Form1 : Form
{
    Random r = new Random();
    int num; // you cannot use r there
    int counter = 0;

    public Form1()
    {
        InitializeComponent();
        num = r.Next(0, 100); // you can use r there
    }

    private void Form1_Load(object sender, EventArgs e)
    {

    }

    private void btn1_Click(object sender, EventArgs e)
    {
        counter++;

        if (int.Parse(txt1.Text) > num)
        {
            lbl1.Text = "the number is too high";
            BackColor = SystemColors.HotTrack; // Form1 is the class


        }
        else {
            lbl1.Text = "the number is too low";
            BackColor = SystemColors.MenuHighlight; // Form1 is the class
        }

    }
}