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QueryAccessibilityHelpEventHandler Delegate

Represents the method that will handle the QueryAccessibilityHelp event of a control.

Namespace: System.Windows.Forms
Assembly: System.Windows.Forms (in system.windows.forms.dll)

public delegate void QueryAccessibilityHelpEventHandler (
	Object sender,
	QueryAccessibilityHelpEventArgs e
)
/** @delegate */
public delegate void QueryAccessibilityHelpEventHandler (
	Object sender, 
	QueryAccessibilityHelpEventArgs e
)
JScript supports the use of delegates, but not the declaration of new ones.

Parameters

sender
e

When you create a QueryAccessibilityHelpEventHandler delegate, you identify the method that will handle the event. To associate the event with your event handler, add an instance of the delegate to the event. The event handler is called whenever the event occurs, unless you remove the delegate. For more information about event-handler delegates, see Events and Delegates.

The following code example demonstrates the creation of an accessibility-aware chart control, using the AccessibleObject and Control.ControlAccessibleObject classes to expose accessible information. The control plots two curves along with a legend. The ChartControlAccessibleObject class, which derives from ControlAccessibleObject, is used in the CreateAccessibilityInstance method to provide custom accessible information for the chart control. Because the chart legend is not an actual Control-based control, but instead is drawn by the chart control, it does not include any built-in accessible information. Because of this, the ChartControlAccessibleObject class overrides the GetChild method to return the CurveLegendAccessibleObject that represents accessible information for each part of the legend. When an accessible-aware application uses this control, the control can provide the necessary accessible information.

This code demonstrates using the QueryAccessibilityHelpEventHandler delegate with the QueryAccessibilityHelp event. For the complete code example, see AccessibleObject.

// Overridden to return the custom AccessibleObject 
// for the entire chart.
protected override AccessibleObject CreateAccessibilityInstance() 
{            
    return new ChartControlAccessibleObject(this);
}

// Overridden to return the custom AccessibleObject 
// for the entire chart.
protected AccessibleObject CreateAccessibilityInstance()
{
    return new ChartControlAccessibleObject(this);
} //CreateAccessibilityInstance

Windows 98, Windows 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 .NET Framework does not support all versions of every platform. For a list of the supported versions, see System Requirements.

.NET Framework

Supported in: 2.0, 1.1, 1.0
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