Auto-Complete for Combo Boxes in C#

This is a very simple auto complete logic which is used commonly and I have moved the logic to a Util Class so that the same logic can be applied to all Combo Boxes in the form.

Add the following class to your C# project

using System;
using System.Text;
using System.Windows.Forms;
using System.Data;
using System.Collections.Generic;
using System.Collections;

namespace Utils
{
    class Util
    {
        public static void comboBox_KeyPress(ComboBox ctrl, 
                      IDictionary<String,Boolean> acf, 
                      object sender, KeyPressEventArgs e)
        {
             if (e.KeyChar == (int)Keys.Escape)
            {
                ctrl.SelectedIndex = -1;
                ctrl.Text = "";
                acf[ctrl.Name] = true;
            }
            else if (Char.IsControl(e.KeyChar))
            {
                acf[ctrl.Name] = true;
            }
            else
            {
                acf[ctrl.Name] = false;
            }

        }

        public static void comboBox_TextChanged(
                       ComboBox ctrl,
                       IDictionary<String,Boolean> acf,  
                       object sender, EventArgs e)
        {
            if  ( ctrl.Text != "" && 
                ( ! acf.ContainsKey(ctrl.Name) || 
                  ! acf[ctrl.Name]))
            {
                string matchText = ctrl.Text;
                int match = ctrl.FindString(matchText);
                if (match != -1)
                {
                    ctrl.SelectedIndex = match;
                    ctrl.SelectionStart = matchText.Length;
                    ctrl.SelectionLength = ctrl.Text.Length-
                                        ctrl.SelectionStart;
                }
            }

        }
    }
}

Make sure you have the following import statements inside your form code


using System.Collections.Generic;
using Utils;


Then, at the top of your Form Class , add the following declaration..


IDictionary<String, Boolean> acf = new Dictionary<String, Boolean>();


Then for each combo Box for which you want to have auto complete feature,
add event handlers for the KeyPress & TextChanged events

Just paste the following two lines into the KeyPress event handler


base.OnTextChanged(e);
Util.comboBox_KeyPress(comboBoxCtrlName, acf, sender, e);


Just paste the following two lines into the TextChanged event handler


base.OnTextChanged(e);
Util.comboBox_TextChanged(comboBoxCtrlName, acf, sender, e);


Remember to replace the comboBoxCtrlName with the name of the Combo Box