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CreateParams Class

Encapsulates the information needed when creating a control.

System.Object
  System.Windows.Forms.CreateParams

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

public class CreateParams

The CreateParams type exposes the following members.

  NameDescription
Public methodCreateParamsInitializes a new instance of the CreateParams class.
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  NameDescription
Public propertyCaptionGets or sets the control's initial text.
Public propertyClassNameGets or sets the name of the Windows class to derive the control from.
Public propertyClassStyleGets or sets a bitwise combination of class style values.
Public propertyExStyleGets or sets a bitwise combination of extended window style values.
Public propertyHeightGets or sets the initial height of the control.
Public propertyParamGets or sets additional parameter information needed to create the control.
Public propertyParentGets or sets the control's parent.
Public propertyStyleGets or sets a bitwise combination of window style values.
Public propertyWidthGets or sets the initial width of the control.
Public propertyXGets or sets the initial left position of the control.
Public propertyYGets or sets the top position of the initial location of the control.
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  NameDescription
Public methodEquals(Object)Determines whether the specified Object is equal to the current Object. (Inherited from Object.)
Protected methodFinalizeAllows an object to try to free resources and perform other cleanup operations before it is reclaimed by garbage collection. (Inherited from Object.)
Public methodGetHashCodeServes as a hash function for a particular type. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Protected methodMemberwiseCloneCreates a shallow copy of the current Object. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Overrides Object.ToString().)
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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 the CreateWindow and CreateWindowEx functions and the CREATESTRUCT structure documentation in the Windows Platform SDK reference located in the MSDN Library.

NoteNote

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.

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.


using System;
using System.Drawing;
using System.Windows.Forms;
using System.Runtime.InteropServices;
using System.Diagnostics;
using System.IO;
using System.Security.Permissions;

[SecurityPermission(SecurityAction.Demand, UnmanagedCode = true)]
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
        {
            new SecurityPermission(SecurityPermissionFlag.UnmanagedCode).Demand();

            // 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;
        }
    }

    [SecurityPermission(SecurityAction.Demand, UnmanagedCode = true)]
    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);

}


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 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);
        }
    }

}


.NET Framework

Supported in: 4, 3.5, 3.0, 2.0, 1.1, 1.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows XP SP2 x64 Edition, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2

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

Any public static (Shared in Visual Basic) members of this type are thread safe. Any instance members are not guaranteed to be thread safe.

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