Form. Close Метод

Определение

Закрывает форму. Closes the form.

Исключения

Форма была закрыта при создании дескриптора. The form was closed while a handle was being created.

Нельзя вызывать этот метод из события Activated, если свойство WindowState задано как Maximized. You cannot call this method from the Activated event when WindowState is set to Maximized.

Комментарии

При закрытии формы все ресурсы, созданные в объекте, закрываются, и форма удаляется. When a form is closed, all resources created within the object are closed and the form is disposed. Можно предотвратить закрытие формы во время выполнения, обрабатывая Closing событие и установив Cancel свойство объекта, CancelEventArgs переданного в качестве параметра обработчику событий. You can prevent the closing of a form at run time by handling the Closing event and setting the Cancel property of the CancelEventArgs passed as a parameter to your event handler. Если закрываемая форма является начальной формой приложения, приложение завершается. If the form you are closing is the startup form of your application, your application ends.

Два условия, когда форма не удаляется Close , имеет значение, если (1) она является частью приложения с многодокументным интерфейсом (MDI), а форма не видна, и (2) форма была отображена с помощью ShowDialog . The two conditions when a form is not disposed on Close is when (1) it is part of a multiple-document interface (MDI) application, and the form is not visible; and (2) you have displayed the form using ShowDialog. В таких случаях необходимо вручную вызвать, Dispose чтобы пометить все элементы управления формы для сборки мусора. In these cases, you will need to call Dispose manually to mark all of the form’s controls for garbage collection.

C# Windows Form: On Close Do [Process]

How can I get my windows form to do something when it is closed.

6 Answers 6

Handle the FormClosed event.

To do that, go to the Events tab in the Properties window and double-click the FormClosed event to add a handler for it.

You can then put your code in the generated MyForm_FormClosed handler.

You can also so this by overriding the OnFormClosed method; to do that, type override onformcl in the code window and OnFormClosed from IntelliSense.

If you want to be able to prevent the form from closing, handle the FormClosing event instead, and set e.Cancel to true .

Or another alternative is to override the OnFormClosed() or OnFormClosing() methods from System.Windows.Forms.Form.

Whether you should use this method depends on the context of the problem, and is more usable when the form will be sub classed several times and they all need to perform the same code.

Events are more useful for one or two instances if you’re doing the same thing.

WinForms has two events that you may want to look at.

The first, the FormClosing event, happens before the form is actually closed. In this event, you can still access any controls and variables in the form’s class. You can also cancel the form close by setting e.Cancel = true; (where e is a System.Windows.Forms.FormClosingEventArgs sent as the second argument to FormClosing ).

The second, the FormClosed event, happens after the form is closed. At this point, you can’t access any controls that the form had, although you can still do cleanup on variables (such as Closing managed resources).

C# Form.Close vs Form.Dispose

I am new to C#, and I tried to look at the earlier posts but did not find a good answer.

In a C# Windows Form Application with a single form, is using Form.Close() better or Form.Dispose() ?

MSDN says that all resources within the object are closed and the form is disposed when a Close is invoked. Inspite of which, I have come across several examples online which follow a Dispose rather than a Close.

Does one have an advantage over the other? Under which scenarios should we prefer one over the other?

7 Answers 7

This forum on MSDN tells you.

Form.Close() sends the proper Windows messages to shut down the win32 window. During that process, if the form was not shown modally, Dispose is called on the form. Disposing the form frees up the unmanaged resources that the form is holding onto.

If you do a form1.Show() or Application.Run(new Form1()) , Dispose will be called when Close() is called.

However, if you do form1.ShowDialog() to show the form modally, the form will not be disposed, and you’ll need to call form1.Dispose() yourself. I believe this is the only time you should worry about disposing the form yourself.

As a general rule, I’d always advocate explicitly calling the Dispose method for any class that offers it, either by calling the method directly or wrapping in a «using» block.

Most often, classes that implement IDisposible do so because they wrap some unmanaged resource that needs to be freed. While these classes should have finalizers that act as a safeguard, calling Dispose will help free that memory earlier and with lower overhead.

In the case of the Form object, as the link fro Kyra noted, the Close method is documented to invoke Dispose on your behalf so you need not do so explicitly. However, to me, that has always felt like relying on an implementaion detail. I prefer to always call both Close and Dispose for classes that implement them, to guard against implementation changes/errors and for the sake of being clear. A properly implemented Dispose method should be safe to invoke multiple times.

Form. Closing Event

Definition

Occurs when the form is closing.

Event Type

Examples

The following example uses Closing to test if the text in a TextBox has changed. If it has, the user is asked whether to save the changes to a file.

Remarks

The Closing event is obsolete starting with the .NET Framework 2.0; use the FormClosing event instead.

The Closing event occurs as the form is being closed. When a form is closed, all resources created within the object are released and the form is disposed. If you cancel this event, the form remains opened. To cancel the closure of a form, set the Cancel property of the CancelEventArgs passed to your event handler to true .

When a form is displayed as a modal dialog box, clicking the Close button (the button with an X at the upper-right corner of the form) causes the form to be hidden and the DialogResult property to be set to DialogResult.Cancel . You can override the value assigned to the DialogResult property when the user clicks the Close button by setting the DialogResult property in an event handler for the Closing event of the form.

When the Close method is called on a Form displayed as a modeless window, you cannot call the Show method to make the form visible, because the form’s resources have already been released. To hide a form and then make it visible, use the Control.Hide method.

The Form.Closed and Form.Closing events are not raised when the Application.Exit method is called to exit your application. If you have validation code in either of these events that must be executed, you should call the Form.Close method for each open form individually before calling the Exit method.

If the form is an MDI parent form, the Closing events of all MDI child forms are raised before the MDI parent form’s Closing event is raised. In addition, the Closed events of all MDI child forms are raised before the Closed event of the MDI parent form is raised. Canceling the Closing event of an MDI child form does not prevent the Closing event of the MDI parent form from being raised. However, canceling the event will set to true the Cancel property of the CancelEventArgs that is passed as a parameter to the parent form. To force all MDI parent and child forms to close, set the Cancel property to false in the MDI parent form.

For more information about handling events, see Handling and Raising Events.

Form. Closing Событие

Определение

Происходит при закрытии формы. Occurs when the form is closing.

Тип события

Примеры

В следующем примере используется Closing для проверки, изменился ли текст в TextBox . The following example uses Closing to test if the text in a TextBox has changed. Если это так, пользователю будет предложено сохранить изменения в файл. If it has, the user is asked whether to save the changes to a file.

Комментарии

ClosingСобытие является устаревшим, начиная с платформа .NET Framework 2,0; FormClosing вместо этого используйте событие. The Closing event is obsolete starting with the .NET Framework 2.0; use the FormClosing event instead.

Это Closing событие возникает при закрытии формы. The Closing event occurs as the form is being closed. Когда форма закрывается, освобождаются все ресурсы, созданные в объекте, и форма удаляется. When a form is closed, all resources created within the object are released and the form is disposed. Если отменить это событие, форма останется открытой. If you cancel this event, the form remains opened. Чтобы отменить закрытие формы, задайте для Cancel свойства объекта, CancelEventArgs переданного обработчику событий, значение true . To cancel the closure of a form, set the Cancel property of the CancelEventArgs passed to your event handler to true .

Когда форма отображается как модальное диалоговое окно, нажатие кнопки Закрыть (кнопка с крестиком в правом верхнем углу формы) приводит к скрытию формы и свойству, для которого DialogResult устанавливается значение DialogResult.Cancel . When a form is displayed as a modal dialog box, clicking the Close button (the button with an X at the upper-right corner of the form) causes the form to be hidden and the DialogResult property to be set to DialogResult.Cancel . Можно переопределить значение, присваиваемое DialogResult свойству, когда пользователь нажимает кнопку Закрыть , задавая DialogResult свойство в обработчике событий для события в Closing форме. You can override the value assigned to the DialogResult property when the user clicks the Close button by setting the DialogResult property in an event handler for the Closing event of the form.

При Close вызове метода для, Form отображаемого в виде немодального окна, нельзя вызвать Show метод, чтобы сделать форму видимой, поскольку ресурсы формы уже были освобождены. When the Close method is called on a Form displayed as a modeless window, you cannot call the Show method to make the form visible, because the form’s resources have already been released. Чтобы скрыть форму и сделать ее видимой, используйте Control.Hide метод. To hide a form and then make it visible, use the Control.Hide method.

Form.ClosedСобытия и Form.Closing не вызываются при Application.Exit вызове метода для выхода из приложения. The Form.Closed and Form.Closing events are not raised when the Application.Exit method is called to exit your application. При наличии кода проверки в любом из этих событий, которые необходимо выполнить, следует вызывать Form.Close метод для каждой открытой формы по отдельности перед вызовом Exit метода. If you have validation code in either of these events that must be executed, you should call the Form.Close method for each open form individually before calling the Exit method.

Если форма является родительской MDI-формой, то Closing события всех дочерних форм MDI создаются до возникновения события родительской формы MDI Closing . If the form is an MDI parent form, the Closing events of all MDI child forms are raised before the MDI parent form’s Closing event is raised. Кроме того, Closed события всех дочерних форм MDI вызываются до того, как Closed будет вызвано событие родительской формы MDI. In addition, the Closed events of all MDI child forms are raised before the Closed event of the MDI parent form is raised. Отмена Closing события дочерней формы MDI не мешает Closing порождению события РОДИТЕЛЬСКОй MDI-формы. Canceling the Closing event of an MDI child form does not prevent the Closing event of the MDI parent form from being raised. Однако при отмене события будет задано true Cancel свойство объекта CancelEventArgs , которое передается в качестве параметра родительской форме. However, canceling the event will set to true the Cancel property of the CancelEventArgs that is passed as a parameter to the parent form. Чтобы принудительно закрыть все родительские и дочерние формы MDI, задайте Cancel для свойства значение false в родительской форме MDI. To force all MDI parent and child forms to close, set the Cancel property to false in the MDI parent form.

Дополнительные сведения об обработке событий см. в разделе обработка и вызов событий. For more information about handling events, see Handling and Raising Events.