EventHandler with FormClosingEventArgs - C#

似乎label7_Click方法不存在

  this.label7.Click += new System.EventHandler(this.label7_Click);
    void label7_Click(object sender, EventArgs e)
    {
    if (MessageBox.Show("Are you sure you want to exit?", "Confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.No)
    {
        //
    }
    else { 
        Application.Exit(); 
    }
    }

'label7_Click'匹配委托没有重载

public void label7_Click(object sender, FormClosingEventArgs e)//this method de is incorrect

Event with FormClosingEventArgs只适用于Form.FormClosing事件。将代码修改为:

public void label7_Click(object sender, EventArgs e)
{
    if (MessageBox.Show("Are you sure you want to exit?", "Confirmation", MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
    {
        this.Close(); //this closes the form
    }
}

您正在尝试将FormClosing事件的事件处理程序设置为标签的单击事件。
这两个事件具有不同的签名，因此是不兼容的。

label_click(object sender, EventArgs e)
MyForm_FormClosing(object sender, FormClosingEventArgs e)

如果你的意图是在用户点击标签时关闭应用程序，那么你需要将事件处理程序更改为

label_click(object sender, EventArgs e)
{
    if (MessageBox.Show("Are you sure you want to exit?", "Confirmation", 
                      MessageBoxButtons.YesNo, MessageBoxIcon.Question) == DialogResult.Yes)
    {
        this.Close();
    }
}

如果你的意图是在用户试图退出应用程序时请求确认，那么你需要添加一个FormClosing事件处理程序到你的表单，然后写入

 MyForm_FormClosing(object sender, FormClosingEventArgs e)
 {
     // NOTE, you don't want to abort closing when Windows shutdown, right?
     if(e.CloseReason == CloseReason.UserClosing)
     {
         if (MessageBox.Show("Are you sure you want to exit?", "Confirmation", 
                            MessageBoxButtons.YesNo, MessageBoxIcon.Question) == 
                            DialogResult.No)
         {
              e.Cancel = true;
         }
     }
 }

声明bool clickStr public bool clickStr = true;

private void label7_Click(object sender, EventArgs e)
{
   clicKStr = false;
   this.Close();
}
private void BeforeFormClosed(object sender, FormClosingEventArgs e)
{
   e.Cancel = clickStr;
}

如果你点击lable7，它将发送false给FormClosingEventArgs并设置cancel为false