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FileDialog.HookProc Method

This member overrides CommonDialog.HookProc(IntPtr, Int32, IntPtr, IntPtr), and more complete documentation might be available in that topic.

Defines the common dialog box hook procedure that is overridden to add specific functionality to the file dialog box.

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

[SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags = SecurityPermissionFlag.UnmanagedCode)]
protected override IntPtr HookProc(
	IntPtr hWnd,
	int msg,
	IntPtr wparam,
	IntPtr lparam


Type: System.IntPtr

The handle to the dialog box window.

Type: System.Int32

The message received by the dialog box.

Type: System.IntPtr

Additional information about the message.

Type: System.IntPtr

Additional information about the message.

Return Value

Type: System.IntPtr
Returns zero if the default dialog box procedure processes the message; returns a nonzero value if the default dialog box procedure ignores the message.

A hook procedure allows the user to connect or insert other routines into a routine or application for the purpose of debugging or enhancing functionality.

By default, the hook procedure centers the dialog box on the screen in response to a WM_INITDIALOG message.

Notes to Inheritors

When overriding HookProc in a derived class, be sure to call the base class's HookProc method.

.NET Framework

Supported in: 4.5.2, 4.5.1, 4.5, 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 8.1, Windows Server 2012 R2, Windows 8, Windows Server 2012, Windows 7, Windows Vista SP2, Windows Server 2008 (Server Core Role not supported), Windows Server 2008 R2 (Server Core Role supported with SP1 or later; Itanium not supported)

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

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