Mick Doherty's .net ComboBox Tips

OwnerDraw ContextMenus do not ownerdraw when assigned to a ComboBox.

With a little help from NativeWindow we can easily overcome this bug.

			VB Code
			
			Imports System.Security.Permissions

Namespace Dotnetrix_Samples

    <ToolboxBitmap(GetType(ComboBox))> _
    Public Class ComboBox
        Inherits System.Windows.Forms.ComboBox

#Region " Windows Form Designer generated code "

        Public Sub New()
            MyBase.New()

            'This call is required by the Windows Form Designer.
            InitializeComponent()

            'Add any initialization after the InitializeComponent() call

        End Sub

        'UserControl1 overrides dispose to clean up the component list.
        Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
            If disposing Then
                If Not (components Is Nothing) Then
                    components.Dispose()
                End If
            End If
                 If Not (Me.Editbox Is Nothing) Then
                    Me.Editbox.ReleaseHandle()
                End If
           MyBase.Dispose(disposing)
        End Sub

        'Required by the Windows Form Designer
        Private components As System.ComponentModel.IContainer

        'NOTE: The following procedure is required by the Windows Form Designer
        'It can be modified using the Windows Form Designer.  
        'Do not modify it using the code editor.
        <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
            components = New System.ComponentModel.Container
        End Sub

#End Region

        Private Const WM_SHOWWINDOW As Int32 = &H18
        Friend Const WM_CONTEXTMENU As Int32 = &H7B
        Private Const WM_CTLCOLOREDIT As Int32 = &H133

        Private Editbox As ComboEdit
        Private cMenu As ContextMenu

        'Disassociate the ContextMenu with the control so we don't get default handling.
        Public Overrides Property ContextMenu() As ContextMenu
            Get
                Return cMenu
            End Get
            Set(ByVal Value As ContextMenu)
                cMenu = Value
                MyBase.ContextMenu = Nothing
                OnContextMenuChanged(EventArgs.Empty)
            End Set
        End Property

        Protected Overrides Sub OnContextMenuChanged(ByVal e As System.EventArgs)
            MyBase.OnContextMenuChanged(e)
            If Me.Editbox Is Nothing Then Return
            Me.Editbox.ContextMenu = cMenu
        End Sub

        <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
        Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
            MyBase.WndProc(m)
            If m.Msg = WM_CTLCOLOREDIT AndAlso Not cMenu Is Nothing Then
                If Me.Editbox Is Nothing Then
                    Me.Editbox = New ComboEdit(m.LParam, Me.Parent)
                End If
            ElseIf m.Msg = WM_CONTEXTMENU AndAlso Not cMenu Is Nothing Then
                Dim pt As Point
                If m.LParam.ToInt32 = -1 Then
                    pt = New Point((Me.Width \ 2) + Me.Left, (Me.Height \ 2) + Me.Top)
                Else
                    pt = Me.Parent.PointToClient(New Point(m.LParam.ToInt32))
                End If

                Me.cMenu.Show(Me.Parent, pt)
            End If
        End Sub

        Private Class ComboEdit
            Inherits NativeWindow

            Public Sub New(ByVal hWnd As IntPtr, ByVal comboParent As Control)
                MyBase.New()
                Me.AssignHandle(hWnd)
                Me.ComboParent = comboParent
            End Sub

            Public [ContextMenu] As ContextMenu
            Private ComboParent As Control

            <PermissionSetAttribute(SecurityAction.Demand, Name:="FullTrust")> _
            Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
                If Not [ContextMenu] Is Nothing Then
                    If m.Msg = WM_CONTEXTMENU Then
                        Me.ContextMenu.Show(ComboParent, ComboParent.PointToClient(New Point(m.LParam.ToInt32)))
                    End If
                End If
                MyBase.WndProc(m)
            End Sub

        End Class

    End Class

End Namespace      
			
C# Code
			
			using System;
using System.Collections;
using System.ComponentModel;
using System.Drawing;
using System.Data;
using System.Windows.Forms;
using System.Security.Permissions;

namespace Dotnetrix_Samples
{
    /// <summary>
    /// Summary description for ComboBox.
    /// </summary>
    public class ComboBox : System.Windows.Forms.ComboBox
    {
        /// <summary>
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;

        public ComboBox()
        {
            // This call is required by the Windows.Forms Form Designer.
            InitializeComponent();

            // TODO: Add any initialization after the InitComponent call

        }

        /// <summary>
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if( components != null )
                    components.Dispose();
                if( this.EditBox != null)
                    this.EditBox.ReleaseHandle();
            }
            base.Dispose( disposing );
        }


        #region Component Designer generated code
        /// <summary>
        /// Required method for Designer support - do not modify 
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            components = new System.ComponentModel.Container();
        }
        #endregion

        private const int WM_SHOWWINDOW = 0x18;
        internal const int WM_CONTEXTMENU = 0x7B;
        private const int WM_CTLCOLOREDIT = 0x133;

        private ComboEdit EditBox;
        private ContextMenu cMenu;

        //Disassociate the ContextMenu with the control so we don't get default handling.
        public override ContextMenu ContextMenu
        {
            get
            {
                return cMenu;
            }
            set
            {
                cMenu = value;
                base.ContextMenu = null;
                this.OnContextMenuChanged(EventArgs.Empty);
            }
        }


        protected override void OnContextMenuChanged(EventArgs e)
        {
            base.OnContextMenuChanged(e);
            if (this.EditBox == null)
                return;
            this.EditBox.ContextMenu = cMenu;
        }


        [PermissionSetAttribute(SecurityAction.Demand, Name="FullTrust")]
        protected override void WndProc(ref System.Windows.Forms.Message m)
        {
            base.WndProc(ref m);
            if (m.Msg == WM_CTLCOLOREDIT && cMenu != null)
            {
                if (this.EditBox == null)
                    this.EditBox = new ComboEdit(m.LParam, this.Parent);
            }
            else if (m.Msg == WM_CONTEXTMENU && cMenu != null)
            {
                Point pt;
                if (m.LParam.ToInt32() == -1)
                    pt = new Point((this.Width / 2) + this.Left, (this.Height / 2) + this.Top);
                else
                    pt = this.Parent.PointToClient(new Point(m.LParam.ToInt32()));
                this.cMenu.Show(this.Parent, pt);
            }
        }

        internal class ComboEdit : NativeWindow
        {
            public ComboEdit(IntPtr hWnd, Control comboParent) : base()
            {
                this.AssignHandle(hWnd);
                this.ComboParent = comboParent;
            }


            public System.Windows.Forms.ContextMenu ContextMenu;
            private System.Windows.Forms.Control ComboParent;

            [PermissionSetAttribute(SecurityAction.Demand, Name="FullTrust")]
            protected override void WndProc(ref Message m)
            {
                if (this.ContextMenu != null)
                    if (m.Msg == WM_CONTEXTMENU)
                        this.ContextMenu.Show(ComboParent, ComboParent.PointToClient(new Point(m.LParam.ToInt32())));
                base.WndProc (ref m);
            }


        }

    }

}
			
			

			

Create an Image Combo.

The following class modifies the Item collection to return a collection of Custom items.
The Property Browser uses the Collection Editor rather than the StringCollection Editor.
The DrawMode property has been hidden, since this property should not be changed.

			VB Code
			
			Imports System.ComponentModel
Imports System.Drawing.Design
Imports System.ComponentModel.Design

Namespace Dotnetrix_Samples

    Public Class ImageCombo
        Inherits System.Windows.Forms.ComboBox

#Region " Windows Form Designer generated code "

        Public Sub New()
            MyBase.New()

            'This call is required by the Windows Form Designer.
            InitializeComponent()

            'Add any initialization after the InitializeComponent() call
            MyBase.DrawMode = DrawMode.OwnerDrawFixed

        End Sub

        'UserControl overrides dispose to clean up the component list.
        Protected Overloads Overrides Sub Dispose(ByVal disposing As Boolean)
            If disposing Then
                If Not (components Is Nothing) Then
                    components.Dispose()
                End If
                If Not (Me.Items Is Nothing) Then
                    For Each o As Object In Me.Items
                        If TypeOf o Is ImageComboItem Then
                            DirectCast(o, ImageComboItem).Dispose()
                        End If
                    Next
                End If
            End If
            MyBase.Dispose(disposing)
        End Sub

        'Required by the Windows Form Designer
        Private components As System.ComponentModel.IContainer

        'NOTE: The following procedure is required by the Windows Form Designer
        'It can be modified using the Windows Form Designer.  
        'Do not modify it using the code editor.
        <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()
            components = New System.ComponentModel.Container
        End Sub

#End Region

        Private currentIndex As Int32 = -1

        <Browsable(False), EditorBrowsable(EditorBrowsableState.Never)> _
        Public Shadows ReadOnly Property DrawMode() As DrawMode
            Get
                Return DrawMode.OwnerDrawFixed
            End Get
        End Property

        <Editor(GetType(ImageComboItemEditor), GetType(UITypeEditor)), _
        DesignerSerializationVisibility(DesignerSerializationVisibility.Content)> _
        Public Shadows ReadOnly Property Items() As ObjectCollection
            Get
                Return MyBase.Items
            End Get
        End Property

        Private Class ImageComboItemEditor
            Inherits CollectionEditor

            Public Sub New(ByVal type As Type)
                MyBase.New(type)
            End Sub

            Protected Overrides Function CreateCollectionItemType() As System.Type
                Return GetType(ImageComboItem)
            End Function

        End Class

        Protected Overrides Sub OnDrawItem(ByVal e As System.Windows.Forms.DrawItemEventArgs)

            If e.Index = -1 OrElse e.Index > Me.Items.Count - 1 Then Return

            e.DrawBackground()

            Dim imageRect As Rectangle = New Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Height, e.Bounds.Height)
            Dim textRectF As RectangleF = RectangleF.FromLTRB(imageRect.Right + 2, e.Bounds.Top, e.Bounds.Right, e.Bounds.Bottom)

            If TypeOf Items(e.Index) Is ImageComboItem Then

                Dim Item As ImageComboItem = DirectCast(Items(e.Index), ImageComboItem)

                If Not (Item.Image Is Nothing) Then
                    e.Graphics.DrawImage(Item.Image, imageRect)
                End If
            End If

            Dim TextBrush As New SolidBrush(Me.ForeColor)
            If (e.State And DrawItemState.Selected) = DrawItemState.Selected Then
                TextBrush.Color = SystemColors.HighlightText
            End If

            Dim sf As New StringFormat(StringFormatFlags.NoWrap)
            sf.LineAlignment = StringAlignment.Center
            sf.Trimming = StringTrimming.EllipsisCharacter

            e.Graphics.DrawString(Items(e.Index).ToString, Me.Font, TextBrush, textRectF, sf)
            TextBrush.Dispose()

        End Sub

        Protected Overrides Sub OnSelectedIndexChanged(ByVal e As System.EventArgs)
            If Me.SelectedIndex <> currentIndex Then
                currentIndex = Me.SelectedIndex
                MyBase.RefreshItem(Me.SelectedIndex)
            Else
                MyBase.OnSelectedIndexChanged(e)
            End If
        End Sub

    End Class

    <DesignTimeVisible(False)> _
    Public Class ImageComboItem
        Inherits Component

        Private m_object As Object
        Private m_Image As Image

        <TypeConverter(GetType(StringConverter))> _
        Public Property [Item]() As Object
            Get
                Return m_object
            End Get
            Set(ByVal Value As Object)
                m_object = Value
            End Set
        End Property

        Public Property [Image]() As Image
            Get
                Return m_Image
            End Get
            Set(ByVal Value As Image)
                m_Image = Value
            End Set
        End Property

        Public Overrides Function ToString() As String
            If m_object Is Nothing Then
                Return String.Empty
            Else
                Return m_object.ToString
            End If
        End Function

    End Class

End Namespace      
			
C# Code
			
			using System;
using System.ComponentModel;
using System.Drawing;
using System.Windows.Forms;

using System.Drawing.Design;
using System.ComponentModel.Design;

namespace Dotnetrix_Samples
{
    /// <summary>
    /// Summary description for ImageCombo.
    /// </summary>
    public class ImageCombo : System.Windows.Forms.ComboBox
    {
        /// <summary> 
        /// Required designer variable.
        /// </summary>
        private System.ComponentModel.Container components = null;

        public ImageCombo()
        {
            // This call is required by the Windows.Forms Form Designer.
            InitializeComponent();

            // TODO: Add any initialization after the InitializeComponent call
            base.DrawMode = DrawMode.OwnerDrawVariable;

        }

        /// <summary> 
        /// Clean up any resources being used.
        /// </summary>
        protected override void Dispose( bool disposing )
        {
            if( disposing )
            {
                if(components != null)
                {
                    components.Dispose();
                }
                if (this.Items != null)
                {
                    foreach (Object o in this.Items)
                    {
                        if (o is ImageComboItem)
                            ((ImageComboItem)o).Dispose();
                    }
                }
            }
            base.Dispose( disposing );
        }

        #region Component Designer generated code
        /// <summary> 
        /// Required method for Designer support - do not modify 
        /// the contents of this method with the code editor.
        /// </summary>
        private void InitializeComponent()
        {
            components = new System.ComponentModel.Container();
        }
        #endregion

        private int currentIndex = -1;

        [Browsable(false), EditorBrowsable(EditorBrowsableState.Never)]
        public new DrawMode DrawMode
        {
            get{return DrawMode.OwnerDrawFixed;}
        }


        [Editor(typeof(ImageComboItemEditor), typeof(UITypeEditor))]
        [DesignerSerializationVisibility(DesignerSerializationVisibility.Content)]
        public new ObjectCollection Items
        {
            get{return base.Items;}
        }


        private class ImageComboItemEditor : CollectionEditor
        {
            public ImageComboItemEditor(Type type):base(type){}

            protected override Type CreateCollectionItemType()
            {
                return typeof(ImageComboItem);
            }


        }


        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            if (e.Index == -1 || e.Index > this.Items.Count - 1)
                return;

            e.DrawBackground();

            Rectangle imageRect = new Rectangle(e.Bounds.X, e.Bounds.Y, e.Bounds.Height, e.Bounds.Height);
            RectangleF textRectF = RectangleF.FromLTRB(imageRect.Right + 2, e.Bounds.Top, e.Bounds.Right, e.Bounds.Bottom);
            
            if (Items[e.Index] is ImageComboItem )
            {
                ImageComboItem Item = (ImageComboItem)Items[e.Index];
                
                if (Item.Image != null)
                    e.Graphics.DrawImage(Item.Image, imageRect);
            }

            SolidBrush TextBrush = new SolidBrush(this.ForeColor);
            if ((e.State & DrawItemState.Selected) == DrawItemState.Selected)
                TextBrush.Color = SystemColors.HighlightText;

            StringFormat sf = new StringFormat(StringFormatFlags.NoWrap);
            sf.LineAlignment = StringAlignment.Center;
            sf.Trimming = StringTrimming.EllipsisCharacter;

            e.Graphics.DrawString(Items[e.Index].ToString(), this.Font, TextBrush, textRectF, sf);
            TextBrush.Dispose();
        }

        protected override void OnSelectedIndexChanged(EventArgs e)
        {
            if (this.SelectedIndex != this.currentIndex)
            {
                this.currentIndex = this.SelectedIndex;
                base.RefreshItem(this.SelectedIndex);
            }
            else
            {
                base.OnSelectedIndexChanged (e);
            }

        }

    }

    [DesignTimeVisible(false)]
    public class ImageComboItem : Component
    {

        private Object m_object;
        private Image m_Image;

        [TypeConverter(typeof(StringConverter))]
        public Object Item
        {
            get{return m_object;}
            set{m_object = value;}
        }

        public Image Image
        {
            get{return m_Image;}
            set{m_Image = value;}
        }

        public override string ToString()
        {
            if (m_object == null)
                return String.Empty;
            else
                return m_object.ToString();
        }


    }

}
			
			

			

RightToLeft support has not been implemented in order to keep things simple, but I'm sure you can figure that out.