主要表格控制和限制 [英] main Form control and restriction

问题描述

C#，Visual Studio
我有一个表格A，其中显示了计数器的值和打开表格B的选项.

当用户单击表单B时，表单B出现两个按钮，
按钮1:增加值，以A形式增加计数器值
按钮2:减少值，以A形式减少计数器值


问题是，当用户创建多个表格B并单击增加或减少时，仅B的第一个实例应增加或减少值，并限制其他形式的表格B来更新计数器.


你们可以在这方面给我链接有用的文章还是帮我吗?

C#,Visual Studio
i have a form A which shows value of counter and option to open form B.

when user clicks on form B, form B appears with two buttons,
button 1 : increase value, increases counter value in form A
button 2 : decrease value, decrease counter value in form A


the problem is that when user creates multiple Form B and click on increase or decreases, only first instance of B should increase or decrease value and restricting other instance of form B to update counter.


Can u guys link me useful articles or help me in this context

推荐答案

在FormB中创建Changed事件:

Create a Changed event in FormB:

public event EventHandler Changed;

protected virtual void OnChanged(EventArgs e)
   {
   EventHandler eh = Changed;
   if (eh != null)
      {
      eh(this, e);
      }
   }

在FormA中创建一个类级别的变量:

Create a class level variable in FormA:

private FormB formB = null;

当要求您打开FormB时:

When you are asked to open FormB:

 if (formB == null)
    {
    formB = new FormB();
    formB.FormClosed += new FormClosedEventHandler(formB_FormClosed);
    formB.Changed += new EventHandler(formB_Changed);
    formB.Show();
    }
else
    {
    formB.Focus();
    }

事件处理程序很简单:

The event handlers are simple:

void formB_Changed(object sender, EventArgs e)
    {
    // ... update counters
    }

void formB_FormClosed(object sender, FormClosedEventArgs e)
    {
    formB = null;
    }

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