Question

很抱歉新手问题，因为我刚刚开始使用C＃。

我有一个班级

namespace WindowsFormsApplication1
{
    class people
    {
        public int Cash;
        public string LastName;
        public void GiveCash(int amount) { this.Cash = this.Cash - amount; }
        public void ReceiveCash(int amount) { this.Cash = this.Cash + amount; }

    }
}

我用它初始化了两个对象。

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        people viktor = new people() { Cash = 1000, LastName = "Jushenko" };
        people julia = new people() { Cash = 500, LastName = "Timoshenko" };
    }

但稍后在代码中我无法访问任何这些对象。例如，我使用

    private void button1_Click(object sender, EventArgs e)
    { viktor.cash = 200; }

它说“在这种背景下不存在名字'胜利者'......”我做错了什么？

谢谢！

Answer 1

您在Form1构造函数中声明局部变量。超出范围后，您无法访问它们。您应该将它们声明为类中的字段，如下所示：

public partial class Form1 : Form
{
    private people viktor;
    private people julia;
    public Form1()
    {
        InitializeComponent();
        viktor = new people() { Cash = 1000, LastName = "Jushenko" };
        julia = new people() { Cash = 500, LastName = "Timoshenko" };
    }

字段viktor和julia现在是您班级的一部分，您可以从班级内的方法访问它们。

Answer 2

victor变量的范围是Form1构造函数的本地范围，无法在其外部访问。

如果要在事件处理程序中访问它，则需要将其提升为字段：

private people viktor;

public Form1()
{
    InitializeComponent();
    viktor = new people() { Cash = 1000, LastName = "Jushenko" };
    people julia = new people() { Cash = 500, LastName = "Timoshenko" };
}

private void button1_Click(object sender, EventArgs e)
{ 
  viktor.cash = 200;
  // Note: the "julia" variable is not in scope here.
}

Answer 3

您需要注意不同的范围。您无法访问变量的原因是因为它们位于您无法访问的范围内。

一种解决方案是将变量移出当前范围：

public partial class Form1 : Form
{
    private people victor = null;
    private people julia = null;
    public Form1()
    {
        InitializeComponent();
        this.viktor = new people() { Cash = 1000, LastName = "Jushenko" };
        this.julia = new people() { Cash = 500, LastName = "Timoshenko" };
    }
....

C＃，对象问题

3 个答案: