让我先来介绍一下背景。
我们有一个中等规模的应用程序，它在各个地方（数百处）使用 MessageBox.Show(...)。
这些消息框是工作流程的一部分，用于通知、警告或从用户那里获取输入。如果没有活动，应用程序应自动注销。我们有一个要求，在注销应用程序时，只需清除会话数据、清除视图并隐藏它本身，以便在下次启动时，不必执行启动过程，该过程在时间成本方面很高。
一切运行良好，但是当屏幕上有某个消息框而用户没有响应该消息框，并且由于没有活动而导致应用程序注销时，问题就出现了。问题是消息框不会消失。
如何在隐藏应用程序的同时关闭打开的消息框（如果有的话）？
这是一段基于UIAutomation的代码（一个酷但仍未被广泛使用的API），它试图关闭当前进程中的所有模态窗口（包括使用MessageBox打开的窗口）：
/// <summary>
/// Attempt to close modal windows if there are any.
/// </summary>
public static void CloseModalWindows()
{
// get the main window
AutomationElement root = AutomationElement.FromHandle(Process.GetCurrentProcess().MainWindowHandle);
if (root == null)
return;
// it should implement the Window pattern
object pattern;
if (!root.TryGetCurrentPattern(WindowPattern.Pattern, out pattern))
return;
WindowPattern window = (WindowPattern)pattern;
if (window.Current.WindowInteractionState != WindowInteractionState.ReadyForUserInteraction)
{
// get sub windows
foreach (AutomationElement element in root.FindAll(TreeScope.Children, new PropertyCondition(AutomationElement.ControlTypeProperty, ControlType.Window)))
{
// hmmm... is it really a window?
if (element.TryGetCurrentPattern(WindowPattern.Pattern, out pattern))
{
// if it's ready, try to close it
WindowPattern childWindow = (WindowPattern)pattern;
if (childWindow.Current.WindowInteractionState == WindowInteractionState.ReadyForUserInteraction)
{
childWindow.Close();
}
}
}
}
}
private void button1_Click(object sender, EventArgs e)
{
MessageBox.Show("Don't click me. I want to be closed automatically!");
}
protected override void WndProc(ref System.Windows.Forms.Message m)
{
const int WM_SYSCOMMAND = 0x0112;
const int SC_CLOSE = 0xF060;
if (m.Msg == WM_SYSCOMMAND) // this is sent even if a modal MessageBox is shown
{
if ((int)m.WParam == SC_CLOSE)
{
CloseModalWindows();
Close();
}
}
base.WndProc(ref m);
}
WPF应用程序中进行了测试，当计时器滴答作响时，调用了方法CloseModalWindows()，效果非常好，谢谢！ - Paul Efford这个链接在MSDN论坛上展示了如何使用FindWindow和发送WM_CLOSE消息来关闭消息框。虽然该问题是针对.NET/WindowsCE提出的，但它可能解决您的问题，值得一看。
请参考"在若干秒后关闭MessageBox"的DmitryG帖子
在超时到达后自动关闭MessageBox
using System.Runtime.InteropServices;
using System.Threading;
using System.Windows.Forms;
public class AutoClosingMessageBox
{
System.Threading.Timer _timeoutTimer;
string _caption;
AutoClosingMessageBox(string text, string caption, int timeout)
{
_caption = caption;
_timeoutTimer = new System.Threading.Timer(OnTimerElapsed,
null, timeout, System.Threading.Timeout.Infinite);
MessageBox.Show(text, caption);
}
public static void Show(string text, string caption, int timeout)
{
new AutoClosingMessageBox(text, caption, timeout);
}
void OnTimerElapsed(object state)
{
IntPtr mbWnd = FindWindow(null, _caption);
if (mbWnd != IntPtr.Zero)
SendMessage(mbWnd, WM_CLOSE, IntPtr.Zero, IntPtr.Zero);
_timeoutTimer.Dispose();
}
const int WM_CLOSE = 0x0010;
[System.Runtime.InteropServices.DllImport("user32.dll", SetLastError = true)]
static extern IntPtr FindWindow(string lpClassName, string lpWindowName);
[System.Runtime.InteropServices.DllImport("user32.dll", CharSet = System.Runtime.InteropServices.CharSet.Auto)]
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
}
调用它
AutoClosingMessageBox.Show("Content", "Title", TimeOut);
private void button1_Click(object sender, EventArgs e)
{
backgroundWorker1.RunWorkerAsync();
MessageBox.Show("Close this message!");
}
private void backgroundWorker1_DoWork(object sender, DoWorkEventArgs e)
{
Thread.Sleep(5000);
SendKeys.SendWait("{Enter}");//or Esc
}
这个主题在其他SO问题中已经充分涵盖，但由于这个特定的问题有几个关于使用UI自动化/窗口查找技术（我不是特别喜欢）和创建自己的对话框而没有提供代码的通用建议，因此我决定发布自己的解决方案。可以创建一个可实例化的MessageBox类，如下所示：
using System;
using System.Drawing;
using System.Linq;
using System.Windows.Forms;
using System.Text.RegularExpressions;
namespace Common
{
// Loosely based on: https://www.codeproject.com/Articles/17253/A-Custom-Message-Box
class MsgBox : Form
{
private Panel _plHeader = new Panel();
private Panel _plFooter = new Panel();
private Panel _plIcon = new Panel();
private PictureBox _picIcon = new PictureBox();
private FlowLayoutPanel _flpButtons = new FlowLayoutPanel();
private Label _lblMessage;
private MsgBox()
{
FormBorderStyle = FormBorderStyle.FixedDialog;
BackColor = Color.White;
StartPosition = FormStartPosition.CenterScreen;
MinimizeBox = false;
MaximizeBox = false;
ShowIcon = false;
Width = 400;
_lblMessage = new Label();
_lblMessage.Font = new Font("Segoe UI", 10);
_lblMessage.Dock = DockStyle.Fill;
_lblMessage.TextAlign = ContentAlignment.MiddleLeft;
_flpButtons.FlowDirection = FlowDirection.RightToLeft;
_flpButtons.Dock = DockStyle.Fill;
//_plHeader.FlowDirection = FlowDirection.TopDown;
_plHeader.Dock = DockStyle.Fill;
_plHeader.Padding = new Padding(20);
_plHeader.Controls.Add(_lblMessage);
_plFooter.Dock = DockStyle.Bottom;
_plFooter.BackColor = Color.FromArgb(240, 240, 240);
_plFooter.Padding = new Padding(10);
_plFooter.Height = 60;
_plFooter.Controls.Add(_flpButtons);
_picIcon.Location = new Point(30, 50);
_plIcon.Dock = DockStyle.Left;
_plIcon.Padding = new Padding(20);
_plIcon.Width = 70;
_plIcon.Controls.Add(_picIcon);
Controls.Add(_plHeader);
Controls.Add(_plIcon);
Controls.Add(_plFooter);
}
public static DialogResult Show(IWin32Window owner, string message, string title = null, MessageBoxButtons? buttons = MessageBoxButtons.OK, MessageBoxIcon icon = MessageBoxIcon.Information)
{
var msgBox = Create(message, title, buttons, icon);
return msgBox.ShowDialog(owner);
}
public static DialogResult Show(string message, string title = null, MessageBoxButtons? buttons = MessageBoxButtons.OK, MessageBoxIcon icon = MessageBoxIcon.Information)
{
var msgBox = Create(message, title, buttons, icon);
return msgBox.ShowDialog();
}
public static MsgBox Create(string message, string title = null, MessageBoxButtons? buttons = MessageBoxButtons.OK, MessageBoxIcon icon = MessageBoxIcon.Information)
{
var msgBox = new MsgBox();
msgBox.Init(message, title, buttons, icon);
return msgBox;
}
void Init(string message, string title, MessageBoxButtons? buttons, MessageBoxIcon icon)
{
_lblMessage.Text = message;
Text = title;
InitButtons(buttons);
InitIcon(icon);
Size = MessageSize(message);
}
void InitButtons(MessageBoxButtons? buttons)
{
if (!buttons.HasValue)
return;
switch (buttons)
{
case MessageBoxButtons.AbortRetryIgnore:
AddButton("Ignore");
AddButton("Retry");
AddButton("Abort");
break;
case MessageBoxButtons.OK:
AddButton("OK");
break;
case MessageBoxButtons.OKCancel:
AddButton("Cancel");
AddButton("OK");
break;
case MessageBoxButtons.RetryCancel:
AddButton("Cancel");
AddButton("Retry");
break;
case MessageBoxButtons.YesNo:
AddButton("No");
AddButton("Yes");
break;
case MessageBoxButtons.YesNoCancel:
AddButton("Cancel");
AddButton("No");
AddButton("Yes");
break;
}
}
void InitIcon(MessageBoxIcon icon)
{
switch (icon)
{
case MessageBoxIcon.None:
_picIcon.Hide();
break;
case MessageBoxIcon.Exclamation:
_picIcon.Image = SystemIcons.Exclamation.ToBitmap();
break;
case MessageBoxIcon.Error:
_picIcon.Image = SystemIcons.Error.ToBitmap();
break;
case MessageBoxIcon.Information:
_picIcon.Image = SystemIcons.Information.ToBitmap();
break;
case MessageBoxIcon.Question:
_picIcon.Image = SystemIcons.Question.ToBitmap();
break;
}
_picIcon.Width = _picIcon.Image.Width;
_picIcon.Height = _picIcon.Image.Height;
}
private void ButtonClick(object sender, EventArgs e)
{
Button btn = (Button)sender;
switch (btn.Text)
{
case "Abort":
DialogResult = DialogResult.Abort;
break;
case "Retry":
DialogResult = DialogResult.Retry;
break;
case "Ignore":
DialogResult = DialogResult.Ignore;
break;
case "OK":
DialogResult = DialogResult.OK;
break;
case "Cancel":
DialogResult = DialogResult.Cancel;
break;
case "Yes":
DialogResult = DialogResult.Yes;
break;
case "No":
DialogResult = DialogResult.No;
break;
}
Close();
}
private static Size MessageSize(string message)
{
int width=350;
int height = 230;
SizeF size = TextRenderer.MeasureText(message, new Font("Segoe UI", 10));
if (message.Length < 150)
{
if ((int)size.Width > 350)
{
width = (int)size.Width;
}
}
else
{
string[] groups = (from Match m in Regex.Matches(message, ".{1,180}") select m.Value).ToArray();
int lines = groups.Length+1;
width = 700;
height += (int)(size.Height+10) * lines;
}
return new Size(width, height);
}
private void AddButton(string caption)
{
var btn = new Button();
btn.Text = caption;
btn.Font = new Font("Segoe UI", 8);
btn.BackColor = Color.FromArgb(225, 225, 225);
btn.Padding = new Padding(3);
btn.Height = 30;
btn.Click += ButtonClick;
_flpButtons.Controls.Add(btn);
}
}
}
可以将对话框的引用保存在类作用域中，显示对话框并获取结果，或者在应用程序退出事件处理程序中关闭对话框。
MsgBox _msgBox;
void eventHandler1(object sender, EventArgs e)
{
_msgBox = MsgBox.Create("Do you want to continue", "Inquiry", MessageBoxButtons.YesNo);
var result = _msgBox.ShowDialog();
// do something with result
}
void applicationExitHandler(object sender, EventArgs e)
{
if (_msgBox != null)
_msgBox.Close();
}
MessageBox 没有的功能，因此制作自定义的 MessageBox 类非常有用。在其他 SO 回答中，我还发现了一些关于使用 MessageBox.Show() 的 IWin32Window 所有者参数来插入低级别不可见窗口的很酷的解决方案。我也喜欢那种方法，但我无法在短时间内使其足够强大。 - ceztko我认为最干净的方法是实现自己的消息框表单，就像这样：
class MyMessageBox : Form {
private MyMessageBox currentForm; // The currently active message box
public static Show(....) { // same as MessageBox.Show
// ...
}
public static Show(...) { // define additional overloads
}
public static CloseCurrent() {
if (currentForm != null)
currentForm.Close();
}
// ...
}
GetTopWindow()（或者可能是其他WIN32函数）获取您应用程序的当前顶级窗口，并向其发送WM_CLOSE消息。MessageBox.Show(this,"message") 打开 MessageBox。保留表单处理程序并使用以下代码关闭它：
static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);
或者
将表单作为类参数保持，并使用 FormX.Close()。
假设您可以编辑调用MessageBox.Show()方法的代码，我建议不要使用MessageBox。相反，只需使用自己的自定义表单，在其上调用ShowDialog()以执行与MessageBox类基本相同的操作。然后，您就拥有了表单实例本身，并且可以在该实例上调用Close()来关闭它。
一个很好的例子是这里。
msg 表明您可以拥有一个真正的消息框，并在延迟后关闭它... - Joeyprivate int interval = 0;
private string message = "";
public msgBox(string msg = "", int i = 0)
{
InitializeComponent();
interval = i;
message = msg;
}
private void MsgBox_Load(object sender, EventArgs e)
{
if (interval > 0)
timer1.Interval = interval;
lblMessage.Text = message;
lblMessage.Width = panel1.Width - 20;
lblMessage.Left = 10;
}
private void Timer1_Tick(object sender, EventArgs e)
{
this.Close();
}
private void Panel1_Paint(object sender, PaintEventArgs e)
{
ControlPaint.DrawBorder(e.Graphics, this.panel1.ClientRectangle, Color.DarkBlue, ButtonBorderStyle.Solid);
}
在主表单中使用的方法
private void showMessage(string msg, int interval = 0)
{
msgBox mb = new msgBox(msg, interval);
mb.ShowDialog(this);
}
叫它
showMessage("File saved");
MessageBox.Show(...)是模态的，那么程序怎么能发送一个键呢？你是使用线程/任务吗？ - Fischermaen