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TreeView.OnKeyDown Method

Microsoft Silverlight will reach end of support after October 2021. Learn more.

Provides handling for the KeyDown event when a key is pressed while the control has focus.

Namespace:  System.Windows.Controls
Assembly:  System.Windows.Controls (in System.Windows.Controls.dll)

Syntax

'Declaration
Protected Overrides Sub OnKeyDown ( _
    e As KeyEventArgs _
)

protected override void OnKeyDown(
    KeyEventArgs e
)

Parameters

Exceptions

Exception Condition
ArgumentNullException

e is null.

Remarks

The OnKeyDown method is called before any event handler for the KeyDown is called. This method allows derived classes to handle the KeyDown event without attaching a delegate. This is the preferred technique for handling the event in a derived class.

When the Control key is pressed in combination with other keys, the TreeView physically scrolls by pixel. When the same keys are pressed alone; not in combination with the Control, the TreeView control scrolls logically, by item.

This implementation marks the KeyDown event as handled by setting the Handled property of the event data to true in the following situations:

  • The TreeView can scroll, the Control key is pressed, and one of the following keys is pressed:

    Home

    End

    PageUp

    PageDown

    Left

    Right

    Up

    Down

  • The PageUp key is pressed and the TreeView scrolls by page.

  • The Home key is pressed and the control successfully puts focus on the first item.

  • The End key is pressed and the control successfully puts focus on the last item.

  • The Up or Down key is pressed when there is no selected item and the control can focus on the first item.

  • The Left or Right is pressed and the control expands or collapses.

Notes to Inheritors

If you override OnKeyDown, you can prevent registered delegates from receiving events by setting Handled to true. For more information about routed events and the Handled property, see Events Overview for Silverlight.

Version Information

Silverlight

Supported in: 5, 4, 3

Platforms

For a list of the operating systems and browsers that are supported by Silverlight, see Supported Operating Systems and Browsers.