MdiChildActivate Event

Form.MdiChildActivate Event

Occurs when a multiple-document interface (MDI) child form is activated or closed within an MDI application.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in

public event EventHandler MdiChildActivate
/** @event */
public void add_MdiChildActivate (EventHandler value)

/** @event */
public void remove_MdiChildActivate (EventHandler value)

In JScript, you can handle the events defined by a class, but you cannot define your own.
Not applicable.

You can use this event to perform tasks such as updating the contents of the MDI child form and changing the menu options available in the MDI parent form based on the status of the MDI child form that is activated.

For more information about handling events, see Consuming Events.

The following code example demonstrates the use of this member. In the example, an event handler reports on the occurrence of the MdiChildActivate event. This report helps you to learn when the event occurs and can assist you in debugging. To report on multiple events or on events that occur frequently, consider replacing System.Windows.Forms.MessageBox.Show with System.Console.WriteLine or appending the message to a multiline TextBox.

To run the example code, paste it into a project that contains an instance of type Form named Form1. Then ensure that the event handler is associated with the MdiChildActivate event.

private void Form1_MdiChildActivate(Object sender, EventArgs e) {

   MessageBox.Show("You are in the Form.MdiChildActivate event.");


Windows 98, Windows Server 2000 SP4, Windows CE, Windows Millennium Edition, Windows Mobile for Pocket PC, Windows Mobile for Smartphone, Windows Server 2003, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP SP2, Windows XP Starter Edition

The Microsoft .NET Framework 3.0 is supported on Windows Vista, Microsoft Windows XP SP2, and Windows Server 2003 SP1.

.NET Framework

Supported in: 3.0, 2.0, 1.1, 1.0

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