CreateParams Class
Definition
Important
Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.
Encapsulates the information needed when creating a control.
public ref class CreateParams
public class CreateParams
type CreateParams = class
Public Class CreateParams
- Inheritance
-
CreateParams
Examples
The following code example creates a Button derived class named MyIconButton
and provides the implementation needed for the button to display an Icon rather than an Image. The CreateParams property is extended and a value added to the Style property that causes the button to display an Icon rather than an Image.
#include <windows.h>
#using <System.dll>
#using <System.Drawing.dll>
#using <System.Windows.Forms.dll>
using namespace System;
using namespace System::Drawing;
using namespace System::Windows::Forms;
using namespace System::Runtime::InteropServices;
using namespace System::Diagnostics;
using namespace System::IO;
public ref class MyIconButton: public Button
{
private:
Icon^ icon;
public:
MyIconButton()
{
// Set the button's FlatStyle property.
FlatStyle = ::FlatStyle::System;
}
MyIconButton( Icon^ ButtonIcon )
{
// Set the button's FlatStyle property.
FlatStyle = ::FlatStyle::System;
// Assign the icon to the private field.
this->icon = ButtonIcon;
// Size the button to 4 pixels larger than the icon.
this->Height = icon->Height + 4;
this->Width = icon->Width + 4;
}
protected:
property System::Windows::Forms::CreateParams^ CreateParams
{
virtual System::Windows::Forms::CreateParams^ get() override
{
// Extend the CreateParams property of the Button class.
System::Windows::Forms::CreateParams^ cp = __super::CreateParams;
// Update the button Style.
cp->Style |= 0x00000040; // BS_ICON value
return cp;
}
}
public:
property System::Drawing::Icon^ Icon
{
System::Drawing::Icon^ get()
{
return icon;
}
void set(System::Drawing::Icon^ value)
{
icon = value;
UpdateIcon();
this->Height = icon->Height + 4;
this->Width = icon->Width + 4;
}
}
protected:
virtual void OnHandleCreated( EventArgs^ e ) override
{
Button::OnHandleCreated( e );
// Update the icon on the button if there is currently an icon assigned to the icon field.
if ( icon != nullptr )
{
UpdateIcon();
}
}
private:
void UpdateIcon()
{
IntPtr iconHandle = IntPtr::Zero;
// Get the icon's handle.
if ( icon != nullptr )
{
iconHandle = icon->Handle;
}
// Send Windows the message to update the button.
SendMessage( (HWND)Handle.ToPointer(), 0x00F7, 1, (int)iconHandle );
/*BM_SETIMAGE value*/
/*IMAGE_ICON value*/
}
public:
[DllImport("user32.dll")]
static LRESULT SendMessage(HWND hWnd, int msg, int wParam, int lParam);
};
using System;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.IO;
public class MyIconButton : Button
{
private Icon icon;
public MyIconButton()
{
// Set the button's FlatStyle property.
FlatStyle = FlatStyle.System;
}
public MyIconButton(Icon ButtonIcon)
: this()
{
// Assign the icon to the private field.
this.icon = ButtonIcon;
// Size the button to 4 pixels larger than the icon.
this.Height = icon.Height + 4;
this.Width = icon.Width + 4;
}
protected override CreateParams CreateParams
{
get
{
// Extend the CreateParams property of the Button class.
CreateParams cp = base.CreateParams;
// Update the button Style.
cp.Style |= 0x00000040; // BS_ICON value
return cp;
}
}
public Icon Icon
{
get
{
return icon;
}
set
{
icon = value;
UpdateIcon();
// Size the button to 4 pixels larger than the icon.
this.Height = icon.Height + 4;
this.Width = icon.Width + 4;
}
}
protected override void OnHandleCreated(EventArgs e)
{
base.OnHandleCreated(e);
// Update the icon on the button if there is currently an icon assigned to the icon field.
if (icon != null)
{
UpdateIcon();
}
}
private void UpdateIcon()
{
IntPtr iconHandle = IntPtr.Zero;
// Get the icon's handle.
if (icon != null)
{
iconHandle = icon.Handle;
}
// Send Windows the message to update the button.
SendMessage(Handle, 0x00F7 /*BM_SETIMAGE value*/, 1 /*IMAGE_ICON value*/, (int)iconHandle);
}
// Import the SendMessage method of the User32 DLL.
[DllImport("user32.dll", CharSet = CharSet.Auto)]
public static extern IntPtr SendMessage(IntPtr hWnd, int msg, int wParam, int lParam);
}
Imports System.Windows.Forms
Imports System.Drawing
Imports System.IO
Imports System.Security.Permissions
Public Class MyIconButton
Inherits Button
Private ButtonIcon As Icon
Public Sub New()
MyBase.New()
' Set the button's FlatStyle property.
Me.FlatStyle = System.Windows.Forms.FlatStyle.System
End Sub
Public Sub New(ByVal Icon As Icon)
MyBase.New()
' Assign the icon to the private field.
Me.ButtonIcon = Icon
' Size the button to 4 pixels larger than the icon.
Me.Height = ButtonIcon.Height + 4
Me.Width = ButtonIcon.Width + 4
End Sub
Protected Overrides ReadOnly Property CreateParams() As System.Windows.Forms.CreateParams
Get
Dim SecPerm As New SecurityPermission(SecurityPermissionFlag.UnmanagedCode)
SecPerm.Demand()
' Extend the CreateParams property of the Button class.
Dim cp As System.Windows.Forms.CreateParams = MyBase.CreateParams
' Update the button Style.
cp.Style = cp.Style Or &H40 ' BS_ICON value
Return cp
End Get
End Property
Public Property Icon() As Icon
Get
Return ButtonIcon
End Get
Set(ByVal Value As Icon)
ButtonIcon = Value
UpdateIcon()
' Size the button to 4 pixels larger than the icon.
Me.Height = ButtonIcon.Height + 4
Me.Width = ButtonIcon.Width + 4
End Set
End Property
<SecurityPermission(SecurityAction.Demand, UnmanagedCode := True)> _
Protected Overrides Sub OnHandleCreated(ByVal e As EventArgs)
MyBase.OnHandleCreated(e)
' Update the icon on the button if there is currently an icon assigned to the icon field.
If Me.ButtonIcon IsNot Nothing Then
UpdateIcon()
End If
End Sub
Private Sub UpdateIcon()
Dim IconHandle As IntPtr = IntPtr.Zero
' Get the icon's handle.
If Me.Icon IsNot Nothing Then
IconHandle = Icon.Handle
End If
' Send Windows the message to update the button.
' BM_SETIMAGE (second parameter) and IMAGE_ICON (third parameter).
SendMessage(Handle, &HF7, &H1, IconHandle.ToInt32())
End Sub
' Declare the SendMessage function.
Declare Auto Function SendMessage Lib "user32" (ByVal hWnd As IntPtr, _
ByVal msg As Integer, ByVal wParam As Integer, ByVal lParam As Integer) As IntPtr
End Class
The following code example creates an instance of a standard Button control and an instance of the derived control, MyIconButton
, created in the example above. This example requires that there is an Icon file named Default.ico in the same location as the application. When the application starts, the Default
icon is displayed on the MyIconButton
button. If the Default
icon is not present, the button face is blank. When the standard Button is clicked, an OpenFileDialog box will appear so you can select a new Icon to display on the MyIconButton
.
public ref class MyApplication: public Form
{
private:
MyIconButton^ myIconButton;
Button^ stdButton;
OpenFileDialog^ openDlg;
public:
MyApplication()
{
try
{
// Create the button with the default icon.
myIconButton = gcnew MyIconButton( gcnew System::Drawing::Icon( String::Concat( Application::StartupPath, "\\Default.ico" ) ) );
}
catch ( Exception^ ex )
{
// If the default icon does not exist, create the button without an icon.
myIconButton = gcnew MyIconButton;
#if defined(DEBUG)
Debug::WriteLine( ex );
#endif
}
finally
{
stdButton = gcnew Button;
// Add the Click event handlers.
myIconButton->Click += gcnew EventHandler( this, &MyApplication::myIconButton_Click );
stdButton->Click += gcnew EventHandler( this, &MyApplication::stdButton_Click );
// Set the location, text and width of the standard button.
stdButton->Location = Point(myIconButton->Location.X,myIconButton->Location.Y + myIconButton->Height + 20);
stdButton->Text = "Change Icon";
stdButton->Width = 100;
// Add the buttons to the Form.
this->Controls->Add( stdButton );
this->Controls->Add( myIconButton );
}
}
private:
void myIconButton_Click( Object^ /*Sender*/, EventArgs^ /*e*/ )
{
#undef MessageBox
// Make sure MyIconButton works.
MessageBox::Show( "MyIconButton was clicked!" );
}
void stdButton_Click( Object^ /*Sender*/, EventArgs^ /*e*/ )
{
// Use an OpenFileDialog to allow the user to assign a new image to the derived button.
openDlg = gcnew OpenFileDialog;
openDlg->InitialDirectory = Application::StartupPath;
openDlg->Filter = "Icon files (*.ico)|*.ico";
openDlg->Multiselect = false;
openDlg->ShowDialog();
if ( !openDlg->FileName->Equals( "" ) )
{
myIconButton->Icon = gcnew System::Drawing::Icon( openDlg->FileName );
}
}
};
int main()
{
Application::Run( gcnew MyApplication );
}
public class MyApplication : Form
{
private MyIconButton myIconButton;
private Button stdButton;
private OpenFileDialog openDlg;
static void Main()
{
Application.Run(new MyApplication());
}
public MyApplication()
{
try
{
// Create the button with the default icon.
myIconButton = new MyIconButton(new Icon(Application.StartupPath + "\\Default.ico"));
}
catch (Exception ex)
{
// If the default icon does not exist, create the button without an icon.
myIconButton = new MyIconButton();
Debug.WriteLine(ex.ToString());
}
finally
{
stdButton = new Button();
// Add the Click event handlers.
myIconButton.Click += new EventHandler(this.myIconButton_Click);
stdButton.Click += new EventHandler(this.stdButton_Click);
// Set the location, text and width of the standard button.
stdButton.Location = new Point(myIconButton.Location.X, myIconButton.Location.Y + myIconButton.Height + 20);
stdButton.Text = "Change Icon";
stdButton.Width = 100;
// Add the buttons to the Form.
this.Controls.Add(stdButton);
this.Controls.Add(myIconButton);
}
}
private void myIconButton_Click(object Sender, EventArgs e)
{
// Make sure MyIconButton works.
MessageBox.Show("MyIconButton was clicked!");
}
private void stdButton_Click(object Sender, EventArgs e)
{
// Use an OpenFileDialog to allow the user to assign a new image to the derived button.
openDlg = new OpenFileDialog();
openDlg.InitialDirectory = Application.StartupPath;
openDlg.Filter = "Icon files (*.ico)|*.ico";
openDlg.Multiselect = false;
openDlg.ShowDialog();
if (openDlg.FileName != "")
{
myIconButton.Icon = new Icon(openDlg.FileName);
}
}
}
Public Class Form1
Inherits System.Windows.Forms.Form
Friend WithEvents MyStdButton As System.Windows.Forms.Button
Friend WithEvents MyIconButton As MyIconButton
Friend WithEvents OpenDlg As OpenFileDialog
Public Sub New()
MyBase.New()
Try
' Create the button with the default icon.
MyIconButton = New MyIconButton(New Icon(Application.StartupPath + "\Default.ico"))
Catch ex As Exception
' If the default icon does not exist, create the button without an icon.
MyIconButton = New MyIconButton()
System.Diagnostics.Debug.WriteLine(ex.ToString())
Finally
MyStdButton = New Button()
'Set the location, text and width of the standard button.
MyStdButton.Location = New Point(MyIconButton.Location.X, _
MyIconButton.Location.Y + MyIconButton.Height + 20)
MyStdButton.Text = "Change Icon"
MyStdButton.Width = 100
' Add the buttons to the Form.
Me.Controls.Add(MyStdButton)
Me.Controls.Add(MyIconButton)
End Try
End Sub
Public Shared Sub Main()
Application.Run(New Form1())
End Sub
Private Sub MyStdButton_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyStdButton.Click
' Use an OpenFileDialog to allow the user to assign a new image to the derived button.
OpenDlg = New OpenFileDialog()
OpenDlg.InitialDirectory = Application.StartupPath
OpenDlg.Filter = "Icon files (*.ico)|*.ico"
OpenDlg.Multiselect = False
OpenDlg.ShowDialog()
If OpenDlg.FileName <> "" Then
MyIconButton.Icon = New Icon(OpenDlg.FileName)
End If
End Sub
Private Sub MyIconButton_Click(ByVal sender As System.Object, _
ByVal e As System.EventArgs) Handles MyIconButton.Click
' Make sure MyIconButton works.
MessageBox.Show("MyIconButton was clicked!")
End Sub
End Class
Remarks
The information in a CreateParams can be used to pass information about the initial state and appearance of a control. Most Control derived controls override the CreateParams property to pass in the appropriate values or include additional information in the CreateParams.
For more information about creating control parameters, see CreateWindow macro, CreateWindowEx function, and CREATESTRUCT structure.
Note
The constants used to set the Style, ExStyle, and ClassStyle properties are defined in the Winuser.h header file. This file is installed by the Platform SDK or Visual Studio.
Constructors
CreateParams() |
Initializes a new instance of the CreateParams class. |
Properties
Caption |
Gets or sets the control's initial text. |
ClassName |
Gets or sets the name of the Windows class to derive the control from. |
ClassStyle |
Gets or sets a bitwise combination of class style values. |
ExStyle |
Gets or sets a bitwise combination of extended window style values. |
Height |
Gets or sets the initial height of the control. |
Param |
Gets or sets additional parameter information needed to create the control. |
Parent |
Gets or sets the control's parent. |
Style |
Gets or sets a bitwise combination of window style values. |
Width |
Gets or sets the initial width of the control. |
X |
Gets or sets the initial left position of the control. |
Y |
Gets or sets the top position of the initial location of the control. |
Methods
Equals(Object) |
Determines whether the specified object is equal to the current object. (Inherited from Object) |
GetHashCode() |
Serves as the default hash function. (Inherited from Object) |
GetType() |
Gets the Type of the current instance. (Inherited from Object) |
MemberwiseClone() |
Creates a shallow copy of the current Object. (Inherited from Object) |
ToString() |
Returns a string that represents the current object. |
Applies to
See also
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