Control.PreProcessMessage Method (System.Windows.Forms)

Microsoft Developer Network

PreProcessMessage Method

.NET Framework Class Library

Control..::.PreProcessMessage Method

Preprocesses keyboard or input messages within the message loop before they are dispatched.

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

Syntax

Visual Basic (Declaration)

<SecurityPermissionAttribute(SecurityAction.InheritanceDemand, Flags := SecurityPermissionFlag.UnmanagedCode)> _
<SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags := SecurityPermissionFlag.UnmanagedCode)> _
Public Overridable Function PreProcessMessage ( _
    ByRef msg As Message _
) As Boolean

Visual Basic (Usage)

Dim instance As Control
Dim msg As Message
Dim returnValue As Boolean

returnValue = instance.PreProcessMessage(msg)

[SecurityPermissionAttribute(SecurityAction.InheritanceDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
[SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
public virtual bool PreProcessMessage(
    ref Message msg
)

Visual C++

[SecurityPermissionAttribute(SecurityAction::InheritanceDemand, Flags = SecurityPermissionFlag::UnmanagedCode)]
[SecurityPermissionAttribute(SecurityAction::LinkDemand, Flags = SecurityPermissionFlag::UnmanagedCode)]
public:
virtual bool PreProcessMessage(
    Message% msg
)

JScript

public function PreProcessMessage(
    msg : Message
) : boolean

Parameters

msg: Type: System.Windows.Forms..::.Message%
A Message, passed by reference, that represents the message to process. The possible values are WM_KEYDOWN, WM_SYSKEYDOWN, WM_CHAR, and WM_SYSCHAR.

Return Value

Type: System..::.Boolean
true if the message was processed by the control; otherwise, false.

Remarks

PreProcessMessage is called by the application's message loop to preprocess input messages before they are dispatched. Possible values for the msg parameter are WM_KEYDOWN, WM_SYSKEYDOWN, WM_CHAR, and WM_SYSCHAR.

When overriding PreProcessMessage, a control should return true to indicate that it has processed the message. For messages that are not processed by the control, the result of base.PreProcessMessage should be returned. Controls will typically override one of the more specialized methods such as IsInputChar, IsInputKey, ProcessCmdKey, ProcessDialogChar, or ProcessDialogKey instead of overriding PreProcessMessage.

.NET Framework Security

UIPermission
for all windows for inheriting classes to call this method. Associated enumeration: AllWindows value of UIPermissionWindow.
UIPermission
for all windows for the immediate caller to call this method. Associated enumeration: AllWindows value of UIPermissionWindow.

Platforms

Windows 7, Windows Vista, Windows XP SP2, Windows XP Media Center Edition, Windows XP Professional x64 Edition, Windows XP Starter Edition, Windows Server 2008 R2, Windows Server 2008, Windows Server 2003, Windows Server 2000 SP4, Windows Millennium Edition, Windows 98

The .NET Framework and .NET Compact Framework do not support all versions of every platform. For a list of the supported versions, see .NET Framework System Requirements.

Version Information

.NET Framework

Supported in: 3.5, 3.0, 2.0, 1.1, 1.0

Reference

Control Class

Control Members

System.Windows.Forms Namespace