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ComboBoxRenderer Class

Provides methods used to render a combo box control with visual styles. This class cannot be inherited.

System.Object
  System.Windows.Forms.ComboBoxRenderer

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

'Declaration
Public NotInheritable Class ComboBoxRenderer

The ComboBoxRenderer type exposes the following members.

  NameDescription
Public propertyStatic memberIsSupportedGets a value indicating whether the ComboBoxRenderer class can be used to draw a combo box with visual styles.
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  NameDescription
Public methodStatic memberDrawDropDownButtonDraws a drop-down arrow with the current visual style of the operating system.
Public methodStatic memberDrawTextBox(Graphics, Rectangle, ComboBoxState)Draws a text box in the specified state and bounds.
Public methodStatic memberDrawTextBox(Graphics, Rectangle, String, Font, ComboBoxState)Draws a text box in the specified state and bounds, with the specified text.
Public methodStatic memberDrawTextBox(Graphics, Rectangle, String, Font, Rectangle, ComboBoxState)Draws a text box in the specified state and bounds, with the specified text and text bounds.
Public methodStatic memberDrawTextBox(Graphics, Rectangle, String, Font, TextFormatFlags, ComboBoxState)Draws a text box in the specified state and bounds, with the specified text and text formatting.
Public methodStatic memberDrawTextBox(Graphics, Rectangle, String, Font, Rectangle, TextFormatFlags, ComboBoxState)Draws a text box in the specified state and bounds, with the specified text, text formatting, and text bounds.
Public methodEquals(Object)Determines whether the specified object is equal to the current object. (Inherited from Object.)
Public methodGetHashCodeServes as the default hash function. (Inherited from Object.)
Public methodGetTypeGets the Type of the current instance. (Inherited from Object.)
Public methodToStringReturns a string that represents the current object. (Inherited from Object.)
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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

.NET Framework

Supported in: 4.6, 4.5, 4, 3.5, 3.0, 2.0

.NET Framework Client Profile

Supported in: 4, 3.5 SP1

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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