如何知道用户已点击“X”或“关闭”按钮？

假设您要求 WinForms，则可以使用 FormClosing（） 事件。每当窗体关闭时，都会触发事件 FormClosing（）。

若要检测用户是否单击了 X 或 CloseButton，可以通过发送方对象获取它。例如，尝试将发送方强制转换为 Button 控件，并验证其名称“CloseButton”。

private void Form1_FormClosing(object sender, FormClosingEventArgs e) {
    if (string.Equals((sender as Button).Name, @"CloseButton"))
        // Do something proper to CloseButton.
    else
        // Then assume that X has been clicked and act accordingly.
}

否则，我从不需要区分是单击了 X 还是 CloseButton，因为我想对 FormClosing 事件执行特定操作，例如在关闭 MDIContainerForm 之前关闭所有 MdiChildren，或者检查未保存的更改。在这种情况下，根据我的说法，我们不需要与任何一个按钮区分开来。

关闭方式 + 也会触发 FormClosing（） 事件，因为它会向 Form 发送一条消息，提示关闭。您可以通过设置ALTF4

FormClosingEventArgs.Cancel = true. 

在我们的示例中，这将翻译为

e.Cancel = true.

请注意 FormClosing（） 和 FormClosed（） 事件之间的区别。

当窗体收到要关闭的消息时，将发生 FormClosure，并在关闭之前验证它是否有事情要做。

FormClosed 发生在窗体实际关闭时，因此在窗体关闭之后。

这有帮助吗？

您在 MSDN 上找到的枚举只是为了检查用户是否关闭了应用程序，或者是由于关机，还是被任务管理器关闭等......CloseReason

您可以根据原因执行不同的操作，例如：

void Form_FormClosing(object sender, FormClosingEventArgs e)
{
    if(e.CloseReason == CloseReason.UserClosing)
        // Prompt user to save his data

    if(e.CloseReason == CloseReason.WindowsShutDown)
        // Autosave and clear up ressources
}

但就像你猜到的，单击x按钮，或右键单击任务栏并单击“关闭”，或按，等等，这两者之间没有区别。这一切都以 CloseReason.UserClosing 原因告终。AltF4

“X”按钮注册，因此另一个选项是评估 .DialogResult.CancelDialogResult

如果您的窗体上有多个按钮，您可能已经将不同的按钮与每个按钮相关联，这将为您提供区分每个按钮的方法。DialogResult

（例如： ，btnSubmit.DialogResult = DialogResult.OKbtnClose.DialogResult = Dialogresult.Abort)

    public Form1()
    {
        InitializeComponent();

        this.FormClosing += Form1_FormClosing;
    }

    /// <summary>
    /// Override the Close Form event
    /// Do something
    /// </summary>
    /// <param name="sender"></param>
    /// <param name="e"></param>
    private void Form1_FormClosing(Object sender, FormClosingEventArgs e)
    {
        //In case windows is trying to shut down, don't hold the process up
        if (e.CloseReason == CloseReason.WindowsShutDown) return;

        if (this.DialogResult == DialogResult.Cancel)
        {
            // Assume that X has been clicked and act accordingly.
            // Confirm user wants to close
            switch (MessageBox.Show(this, "Are you sure?", "Do you still want ... ?", MessageBoxButtons.YesNo, MessageBoxIcon.Question))
            {
                //Stay on this form
                case DialogResult.No:
                    e.Cancel = true;
                    break;
                default:
                    break;
            }
        }
    }

if (this.DialogResult == DialogResult.Cancel)
        {

        }
        else
        {
            switch (e.CloseReason)
            {
                case CloseReason.UserClosing:
                    e.Cancel = true;
                    break;
            }
        }

如果条件将在用户单击表单上的“X”或关闭按钮时执行。当用户出于任何其他目的单击 Alt+f4 时，可以使用 else

它确定在窗体关闭时何时关闭应用程序（如果您的应用程序未附加到特定窗体）。

    private void MyForm_FormClosed(object sender, FormClosedEventArgs e)
    {
        if (Application.OpenForms.Count == 0) Application.Exit();
    }

您可以尝试从设计中添加事件处理程序，如下所示：在设计视图中打开窗体，打开属性窗口或按 F4，单击事件工具栏按钮查看 Form 对象上的事件，在“行为”组中找到 FormClosing 事件，然后双击它。 参考： https://social.msdn.microsoft.com/Forums/vstudio/en-US/9bdee708-db4b-4e46-a99c-99726fa25cfb/how-do-i-add-formclosing-event?forum=csharpgeneral

我总是在我的应用程序中使用 Form Close 方法，该方法从我的退出按钮、alt + f4 或其他表单关闭事件中捕获 alt + x。在本例中，我的所有类都具有定义为 Private string 的类名，即调用 Form Closing 方法和 Form Closing 方法的 Exit 方法。我还有一个关于表单关闭方法的声明 - 。mstrClsTitle = "grmRexcel"this.FormClosing = My Form Closing Form Closing method name

代码如下：

namespace Rexcel_II
{
    public partial class frmRexcel : Form
    {
        private string mstrClsTitle = "frmRexcel";

        public frmRexcel()
        {
            InitializeComponent();

            this.FormClosing += frmRexcel_FormClosing;
        }

        /// <summary>
        /// Handles the Button Exit Event executed by the Exit Button Click
        /// or Alt + x
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void btnExit_Click(object sender, EventArgs e)
        {            
            this.Close();        
        }


        /// <summary>
        /// Handles the Form Closing event
        /// 
        /// </summary>
        /// <param name="sender"></param>
        /// <param name="e"></param>
        private void frmRexcel_FormClosing(object sender, FormClosingEventArgs e)
        {

            // ---- If windows is shutting down, 
            // ---- I don't want to hold up the process
            if (e.CloseReason == CloseReason.WindowsShutDown) return;
            {

                // ---- Ok, Windows is not shutting down so
                // ---- either btnExit or Alt + x or Alt + f4 has been clicked or
                // ---- another form closing event was intiated
                //      *)  Confirm user wants to close the application
                switch (MessageBox.Show(this, 
                                    "Are you sure you want to close the Application?",
                                    mstrClsTitle + ".frmRexcel_FormClosing",
                                    MessageBoxButtons.YesNo, MessageBoxIcon.Question))
                {

                    // ---- *)  if No keep the application alive 
                    //----  *)  else close the application
                    case DialogResult.No:
                        e.Cancel = true;
                        break;
                    default:
                        break;
                }
            }
        }
    }
}

namespace Test
{
    public partial class Member : Form
    {
        public Member()
        {
            InitializeComponent();
        }

        private bool xClicked = true;

        private void btnClose_Click(object sender, EventArgs e)
        {
            xClicked = false;
            Close();
        }

        private void Member_FormClosing(object sender, FormClosingEventArgs e)
        {
            if (xClicked)
            {
                // user click the X
            } 
            else 
            {
                // user click the close button
            }
        }
    }
}

我同意 -Solution 作为更直接的解决方案。DialogResult

但是，在 VB.NET 中，需要类型转换才能获取 -PropertyCloseReason

    Private Sub MyForm_Closing(sender As Object, e As CancelEventArgs) Handles Me.Closing

        Dim eCast As System.Windows.Forms.FormClosingEventArgs
        eCast = TryCast(e, System.Windows.Forms.FormClosingEventArgs)
        If eCast.CloseReason = Windows.Forms.CloseReason.None Then
            MsgBox("Button Pressed")
        Else
            MsgBox("ALT+F4 or [x] or other reason")
        End If

    End Sub

如何通过单击 X 按钮或调用代码来检测表单是否关闭？Close()

您不能依赖表单关闭事件参数的关闭原因，因为：
如果用户单击标题栏上的 X 按钮或使用 Alt + F4 关闭表单或使用系统菜单关闭表单或


通过调用 Close（） 方法关闭表单，

对于上述所有情况，关闭原因将是 Closed by User （），这不是期望的结果。CloseReason.UserClosing

若要区分窗体是按 X 按钮关闭还是按方法关闭，可以使用以下任一选项：Close

• 处理WM_SYSCOMMAND并检查并设置标志。SC_CLOSE
• 检查 StackTrace 以查看是否有任何帧包含方法调用。Close

示例 1 - 句柄WM_SYSCOMMAND

public bool ClosedByXButtonOrAltF4 {get; private set;}
private const int SC_CLOSE = 0xF060;
private const int WM_SYSCOMMAND = 0x0112;
protected override void WndProc(ref Message msg)
{
    if (msg.Msg == WM_SYSCOMMAND && msg.WParam.ToInt32() == SC_CLOSE)
        ClosedByXButtonOrAltF4 = true;
    base.WndProc(ref msg);
}
protected override void OnShown(EventArgs e)
{
    ClosedByXButtonOrAltF4 = false;
}   
protected override void OnFormClosing(FormClosingEventArgs e)
{
    if (ClosedByXButtonOrAltF4)
        MessageBox.Show("Closed by X or Alt+F4");
    else
        MessageBox.Show("Closed by calling Close()");
}

示例 2 - 检查 StackTrace

protected override void OnFormClosing(FormClosingEventArgs e)
{
    if (new StackTrace().GetFrames().Any(x => x.GetMethod().Name == "Close"))
        MessageBox.Show("Closed by calling Close()");
    else
        MessageBox.Show("Closed by X or Alt+F4");
}

我还必须在表单的“InitializeComponent（）”方法中注册关闭函数：

private void InitializeComponent() {
// ...
this.FormClosing += FrmMain_FormClosing;
// ...
}

我的“FormClosing”函数看起来类似于给定的答案（https://stackoverflow.com/a/2683846/3323790）：

private void FrmMain_FormClosing(object sender, FormClosingEventArgs e) {
    if (e.CloseReason == CloseReason.UserClosing){
        MessageBox.Show("Closed by User", "UserClosing");
    }

    if (e.CloseReason == CloseReason.WindowsShutDown){
        MessageBox.Show("Closed by Windows shutdown", "WindowsShutDown");
    }
}

还有一件事要提：还有一个“FormClosed”函数，它发生在“FormClosing”之后。要使用此功能，请按如下所示进行注册：

this.FormClosed += MainPage_FormClosed;

private void MainPage_FormClosing(object sender, FormClosingEventArgs e)
{
// your code after the form is closed
}

我做过这样的事情。

private void Form_FormClosing(object sender, FormClosingEventArgs e)
    {
        if ((sender as Form).ActiveControl is Button)
        {
            //CloseButton
        }
        else
        {
            //The X has been clicked
        }
    }

这种方法是无效的。

protected override void OnFormClosing(FormClosingEventArgs e)
{
    if (new StackTrace().GetFrames().Any(x => x.GetMethod().Name == "Close"))
        MessageBox.Show("Closed by calling Close()");
    else
        MessageBox.Show("Closed by X or Alt+F4");
}

本页参考。