public partial class Form : Form
 {
  public Form()
  {
  InitializeComponent();
  }
  private void button_Click(object sender, EventArgs e)
  {
  //通过Form的构造函数将Form对象传递到Form中
  Form form = new Form(this);
  form.Show();
  }
 }

public partial class Form : Form
 {
  //首先在Form中定义Form类型字段用来存储Form对象
  Form form=null;
  Random r = new Random();
  public Form()
  {
  InitializeComponent();
  }
  public Form(Form form):this()
  {
  //通过构造方法将Form对象给Form字段赋值
  form = form;
  }
  private void button_Click(object sender, EventArgs e)
  {
  //随机改变Form的背景颜色
  form.BackColor = Color.FromArgb(r.Next(),r.Next(),r.Next());
  }
 }

private string str;//定义的私有变量


 public string STR//为窗体Form2定义的属性
 {
  get //读
  { return str;
  }
  set//写
  {
  str = value;
  }
 }