Implementing an OwnerDrawn ComboBox

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Introduction

Hi there, I've been waiting for ages and ages for someone to kindly post the code for an owner drawn ComboBox but alas, to no avail. That's right, I'm your average, lowly leech and I've been stealing code off CodeProject for a long time now. Well looks like this time I actually had to go write something on my own. My guess is it was too simple a problem for most of you to bother with. But please do keep writing articles for relative beginners because most of us have to start with the simple things first. Luckily, writing the code turned out to be childs play with the .NET framework.

Ok, lets begin. First thing to do is drop a ComboBox onto a form and change it's DrawMode property to OwnerDrawFixed. This will mean that all the items appearing in the ComboBox will have the same dimensons. If you're going to draw items in the ComboBox that are of variable sizes then you would change the property to OwnerDrawVariable and be forced to deal with a MeasureItem event. I won't be covering that here. Next, create a DataSource for the ComboBox, as well as a corresponding collection of images. In my case I simply used two Arrays The following code should now be easy enough to follow

The Code

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Data;

namespace WindowsApplication7
{    
    public class Form1 : System.Windows.Forms.Form
    {        
        private System.ComponentModel.Container components = null;
        private String[] arr;
        private Image[] imageArr;
        private System.Windows.Forms.ComboBox comboBox1;        
        public Font myFont;        
        
        public Form1()
        {            
            InitializeComponent();
            myFont = new System.Drawing.Font("Comic Sans", 11);
            
            arr = new String[4];
            arr[0] = "Smiley Red Face";
            arr[1] = "Smiley Cry";
            arr[2] = "Smiley Big Grin";
            arr[3]  = "Smiley Suss";
            
            this.comboBox1.DataSource = arr; //set the combo's data source to out array

            imageArr = new Image[4];

            /* I stole these images off CP. I specifically chose these images because they 
            are all little 16x16 sized gifs. If you're going to use your own images make 
            sure they are all the same size, otherwise your code won't work as advertised. 
            In that case you will have to set the DrawMode property of your combobox to 
            OwnnerDrawVariable and catch the MeasureItem event*/

            imageArr[0] = new Bitmap("C:\\smiley_redface.gif");
            imageArr[1] = new Bitmap("C:\\smiley_cry.gif");
            imageArr[2] = new Bitmap("C:\\smiley_biggrin.gif");
            imageArr[3] = new Bitmap("C:\\smiley_suss.gif");
        }        
        
        //You have your windows forms designer generated code here

        [STAThread]
        static void Main() 
        {
            Application.Run(new Form1());
        }

        private void comboBox1_DrawItem(object sender, 
                                        System.Windows.Forms.DrawItemEventArgs e)
        {    
            // Let's highlight the currently selected item like any well 
            // behaved combo box should
            e.Graphics.FillRectangle(Brushes.Bisque, e.Bounds);                
            e.Graphics.DrawString(arr[e.Index], myFont, Brushes.Blue, 
                                  new Point(imageArr[e.Index].Width*2,e.Bounds.Y));       
            e.Graphics.DrawImage(imageArr[e.Index], new Point(e.Bounds.X, e.Bounds.Y));   
            
            //is the mouse hovering over a combobox item??            
            if((e.State & DrawItemState.Focus)==0)
            {                                                    
                //this code keeps the last item drawn from having a Bisque background. 
                e.Graphics.FillRectangle(Brushes.White, e.Bounds);                    
                e.Graphics.DrawString(arr[e.Index], myFont, Brushes.Blue, 
                                      new Point(imageArr[e.Index].Width*2,e.Bounds.Y));
                e.Graphics.DrawImage(imageArr[e.Index], new Point(e.Bounds.X, e.Bounds.Y)); 
            }    
        }                                                                
    }
}

Conclusion

Ok, that's it, my very first CodeProject article, go easy on me. The code started out quite long and tedious but I whittled it down as my understanding of DrawItemEventArgs became a bit clearer. I'm not too sure if it's cool to have the ComboBox default backcolor to be anything other than white. But that seems to be more a matter of taste.

Regards, Senkwe

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