Where's the ImageCombo control?

• Download source and demo project - 14.4 Kb

Introduction

When I started programming in .NET, I wondered where the ImageCombo control had gone (I used to program in VB6). The .NET Framework didn't seem to have this functionality built-in, but it's very easy to add it.

Using the code

The code consists of two classes: ImageCombo and ImageComboItem. If you want to use them in C#, just copy them into your project; for other .NET languages, you can add a reference to the library.

The control inherits from ComboBox and introduces one new member: the ImageList property, which doesn't require any further explanation. The control is owner drawn and there is a custom drawing method defined, so don't change its DrawMode property if you want to see the images.

The ImageComboItem class inherits from Object. You can set a customForeColor and it has a Mark property which determines if the item is shown in bold font style (does not work if owner font is already bold).

To add an item to an ImageCombo with text "Icon 0" and image index 0, use the following code:

imageCombo.Items.Add(new ImageComboItem("Icon 0", 0));

Code listing: ImageCombo class

using System;
using System.Drawing;

namespace System.Windows.Forms
{

    public class ImageCombo : ComboBox
    {
        private ImageList imgs = new ImageList();

        // constructor
        public ImageCombo()
        {
            // set draw mode to owner draw
            this.DrawMode = DrawMode.OwnerDrawFixed;    
        }

        // ImageList property
        public ImageList ImageList 
        {
            get 
            {
                return imgs;
            }
            set 
            {
                imgs = value;
            }
        }

        // customized drawing process
        protected override void OnDrawItem(DrawItemEventArgs e)
        {
            // draw background & focus rect
            e.DrawBackground();
            e.DrawFocusRectangle();

            // check if it is an item from the Items collection
            if (e.Index < 0)

                // not an item, draw the text (indented)
                e.Graphics.DrawString(this.Text, e.Font, 
                        new SolidBrush(e.ForeColor), e.Bounds.Left + 
                        imgs.ImageSize.Width, e.Bounds.Top);

            else
            {
                
                // check if item is an ImageComboItem
                if (this.Items[e.Index].GetType() == typeof(ImageComboItem)) 
                {                                                            

                    // get item to draw
                    ImageComboItem item = (ImageComboItem) 
                        this.Items[e.Index];

                    // get forecolor & font
                    Color forecolor = (item.ForeColor != 
                         Color.FromKnownColor(KnownColor.Transparent)) ? 
                         item.ForeColor : e.ForeColor;
                    Font font = item.Mark ? new Font(e.Font, 
                         FontStyle.Bold) : e.Font;

                    // -1: no image
                    if (item.ImageIndex != -1) 
                    {
                        // draw image, then draw text next to it
                        this.ImageList.Draw(e.Graphics, 
                           e.Bounds.Left, e.Bounds.Top, item.ImageIndex);
                        e.Graphics.DrawString(item.Text, font, 
                           new SolidBrush(forecolor), e.Bounds.Left + 
                           imgs.ImageSize.Width, e.Bounds.Top);
                    }
                    else
                        // draw text (indented)
                        e.Graphics.DrawString(item.Text, font, 
                            new SolidBrush(forecolor), e.Bounds.Left + 
                            imgs.ImageSize.Width, e.Bounds.Top);

                }
                else
                
                    // it is not an ImageComboItem, draw it
                    e.Graphics.DrawString(this.Items[e.Index].ToString(), 
                      e.Font, new SolidBrush(e.ForeColor), e.Bounds.Left + 
                      imgs.ImageSize.Width, e.Bounds.Top);
                
            }

            base.OnDrawItem (e);
        }
        
    }

}

Code listing: ImageComboItem class

using System;
using System.Drawing;

namespace System.Windows.Forms
{

    public class ImageComboItem : object
    {
        // forecolor: transparent = inherit
        private Color forecolor = Color.FromKnownColor(
                KnownColor.Transparent);
        private bool mark = false;
        private int imageindex = -1;
        private object tag = null;
        private string text = null;        
        
        // constructors
        public ImageComboItem()
        {
        }

        public ImageComboItem(string Text) 
        {
            text = Text;    
        }

        public ImageComboItem(string Text, int ImageIndex)
        {
            text = Text;
            imageindex = ImageIndex;
        }

        public ImageComboItem(string Text, int ImageIndex, bool Mark)
        {
            text = Text;
            imageindex = ImageIndex;
            mark = Mark;
        }

        public ImageComboItem(string Text, int ImageIndex, 
            bool Mark, Color ForeColor)
        {
            text = Text;
            imageindex = ImageIndex;
            mark = Mark;
            forecolor = ForeColor;
        }

        public ImageComboItem(string Text, int ImageIndex, 
               bool Mark, Color ForeColor, object Tag)
        {
            text = Text;
            imageindex = ImageIndex;
            mark = Mark;
            forecolor = ForeColor;
            tag = Tag;
        }

        // forecolor
        public Color ForeColor 
        {
            get 
            {
                return forecolor;
            }
            set
            {
                forecolor = value;
            }
        }

        // image index
        public int ImageIndex 
        {
            get 
            {
                return imageindex;
            }
            set 
            {
                imageindex = value;
            }
        }

        // mark (bold)
        public bool Mark
        {
            get
            {
                return mark;
            }
            set
            {
                mark = value;
            }
        }

        // tag
        public object Tag
        {
            get
            {
                return tag;
            }
            set
            {
                tag = value;
            }
        }

        // item text
        public string Text 
        {
            get
            {
                return text;
            }
            set
            {
                text = value;
            }
        }
        
        // ToString() should return item text
        public override string ToString() 
        {
            return text;
        }

    }

}

History

• Original code (01/10/2004)
• Optimized code for speed & added some functionality (18/10/2004)