ComboBoxRenderer Class
Assembly: System.Windows.Forms (in system.windows.forms.dll)
The ComboBoxRenderer class provides a set of static methods that can be used to render a combo box control with the current visual style of the operating system. Rendering a control refers to drawing the user interface of a control. This is useful if you are drawing a custom control that should have the appearance of the current visual style. To draw a combo box, use the DrawTextBox method to draw the text box and the DrawDropDownButton method to draw the drop-down arrow.
If visual styles are enabled in the operating system and visual styles are applied to the client area of application windows, DrawTextBox and DrawDropDownButton will draw the combo box with the current visual style. Otherwise, these methods will throw an InvalidOperationException. To determine whether the members of this class can be used, you can check the value of the IsSupported property.
This class wraps the functionality of a System.Windows.Forms.VisualStyles.VisualStyleRenderer that is set to one of the elements exposed by the System.Windows.Forms.VisualStyles.VisualStyleElement.ComboBox.DropDownButton and System.Windows.Forms.VisualStyles.VisualStyleElement.TextBox.TextEdit classes. For more information, see Rendering Controls with Visual Styles.
Windows XP Home Edition, Windows XP Professional x64 Edition, Windows Server 2003 Platform Note: Visual styles are supported only on these platforms.
The following code example demonstrates how to create a custom control that uses the DrawTextBox and DrawDropDownButton methods to draw a combo box that responds to mouse clicks.
Imports System Imports System.Drawing Imports System.Windows.Forms Imports System.Windows.Forms.VisualStyles Namespace ComboBoxRendererSample Class Form1 Inherits Form Public Sub New() Me.Size = New Size(300, 300) Dim ComboBox1 As New CustomComboBox() Controls.Add(ComboBox1) End Sub <STAThread()> _ Shared Sub Main() ' The call to EnableVisualStyles below does not affect ' whether ComboBoxRenderer.IsSupported is true; as long as visual ' styles are enabled by the operating system, IsSupported is true. Application.EnableVisualStyles() Application.Run(New Form1()) End Sub End Class Public Class CustomComboBox Inherits Control Private arrowSize As Size Private arrowRectangle As Rectangle Private topTextBoxRectangle As Rectangle Private bottomTextBoxRectangle As Rectangle Private textBoxState As ComboBoxState = ComboBoxState.Normal Private arrowState As ComboBoxState = ComboBoxState.Normal Private bottomText As String = "Using ComboBoxRenderer" Private isActivated As Boolean = False Private minHeight As Integer = 38 Private minWidth As Integer = 40 Public Sub New() Me.Location = New Point(10, 10) Me.Size = New Size(140, 38) Me.Font = SystemFonts.IconTitleFont Me.Text = "Click the button" ' Initialize the rectangles to look like the standard combo ' box control. arrowSize = New Size(18, 20) arrowRectangle = New Rectangle(Me.ClientRectangle.X + _ Me.ClientRectangle.Width - arrowSize.Width - 1, _ Me.ClientRectangle.Y + 1, arrowSize.Width, _ arrowSize.Height) topTextBoxRectangle = New Rectangle(Me.ClientRectangle.X, _ Me.ClientRectangle.Y, Me.ClientRectangle.Width, _ arrowSize.Height + 2) bottomTextBoxRectangle = New Rectangle(Me.ClientRectangle.X, _ Me.ClientRectangle.Y + topTextBoxRectangle.Height, _ Me.ClientRectangle.Width, topTextBoxRectangle.Height - 6) End Sub ' Draw the combo box in the current state. Protected Overrides Sub OnPaint(ByVal e As PaintEventArgs) MyBase.OnPaint(e) If Not ComboBoxRenderer.IsSupported Then Me.Parent.Text = "Visual Styles Disabled" Return End If Me.Parent.Text = "CustomComboBox Enabled" ' Always draw the main text box and drop down arrow in their ' current states. ComboBoxRenderer.DrawTextBox(e.Graphics, topTextBoxRectangle, _ Me.Text, Me.Font, textBoxState) ComboBoxRenderer.DrawDropDownButton(e.Graphics, arrowRectangle, _ arrowState) ' Only draw the bottom text box if the arrow has been clicked. If isActivated Then ComboBoxRenderer.DrawTextBox(e.Graphics, _ bottomTextBoxRectangle, bottomText, Me.Font, textBoxState) End If End Sub Protected Overrides Sub OnMouseDown(ByVal e As MouseEventArgs) MyBase.OnMouseDown(e) ' Check whether the user clicked the arrow. If arrowRectangle.Contains(e.Location) And _ ComboBoxRenderer.IsSupported Then ' Draw the arrow in the pressed state. arrowState = ComboBoxState.Pressed ' The user has activated the combo box. If Not isActivated Then Me.Text = "Clicked!" textBoxState = ComboBoxState.Pressed isActivated = True ' The user has deactivated the combo box. Else Me.Text = "Click here" textBoxState = ComboBoxState.Normal isActivated = False End If ' Redraw the control. Invalidate() End If End Sub Protected Overrides Sub OnMouseUp(ByVal e As MouseEventArgs) MyBase.OnMouseUp(e) If arrowRectangle.Contains(e.Location) And _ ComboBoxRenderer.IsSupported Then arrowState = ComboBoxState.Normal Invalidate() End If End Sub End Class End Namespace
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.