关闭表格C＃时，单击“是”两次。

Question

I write a code for event close form C#. It works, but when I click "yes" to close form I must click twice. What wrong with it? And how can I fix this problem? Here is my code

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
        DialogResult result = MessageBox.Show("Sure?", "Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
        if (result == DialogResult.No)
        {
            Application.Exit();   
        }
        else
        {
            e.Cancel = true;
        }
    }

Answer 1

Your logic right now will run e.Cancel = true if you click yes, as in it cancels the closing.

Also, as mentioned in the comments, Application.Exit() is not necessary.

Answer 2

private void Form1_FormClosing(object sender, FormClosingEventArgs e)
{
    DialogResult result = MessageBox.Show("Sure?", "Exit", MessageBoxButtons.YesNo, MessageBoxIcon.Question);
    if (result != DialogResult.Yes)
        e.Cancel = true;
}

Answer 3

A simpler version would be something like this:

 private void Form1_FormClosing(object sender, FormClosingEventArgs e)
 {
     e.Cancel = (MessageBox.Show("Sure?", 
                                 "Exit", 
                                 MessageBoxButtons.YesNo, 
                                 MessageBoxIcon.Question) == DialogResult.Yes);
 }

If the use clicks the Yes button, then e.Cancel will be set to true.
If e.Cancel is set to true, the form will not close.
otherwise let the form closing sequence run it's course.

Answer 4

Calling the Application.Exit will trigger the FormClosing event again. The solution is easier than you think:

if (result == DialogResult.No)
    {
        e.Cancel = false; //It works as you expected 
    }
    else
    {
        e.Cancel = true;
    }