How to disable the automatic selection of the first item in ComboBox?

Question

I have a form with a ComboBox, which is populated with 3 items.
When I add the statements: comboBox1.Text = "A"; and comboBox1.DroppedDown = true;
the first item of the drop-down list is automatically selected: the comboBox1.Text shows "Abc" in stead of "A".
Here is the code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace testComboBox
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        
            comboBox1 = new ComboBox();
            PopulateComboBox();            
            comboBox1.Location = new Point((this.Width - comboBox1.Width) / 2, 80);            
            this.Controls.Add(comboBox1);

            comboBox1.Text = "A";
            comboBox1.DroppedDown = true;
        }

        ComboBox comboBox1;

        private void PopulateComboBox()
        {
            comboBox1.Items.Add("Abc");
            comboBox1.Items.Add("Abcd");
            comboBox1.Items.Add("Abcde");
        }

        private void button_Exit_Click(object sender, EventArgs e)
        {
            this.Close();
        }
    }
}

How can I disable the automatic selection of the first item in the Items collection of the ComboBox, so that the comboBox1.Text will show "A" and not "Abc"?
I am not looking for a one-time work-around. I need a GENERAL SOLUTION.

Invert the assignments: `comboBox1.DroppedDown = true; comboBox1.Text = "A";`. Move these lines to the `Load` event / `OnLoad()` method. Or `OnShown()` (probably better). — Jimi, Feb 19 '21 at 13:23
https://stackoverflow.com/questions/60107053/stop-changing-text-when-combobox-is-dropped-down/60123714#60123714 — Loathing, Feb 19 '21 at 22:17
@Loathing I am very grateful to you for your comment. I saw in the thread: Prevent AutoSelect behavior of a ystem.Window.Forms.ComboBox (C#) that the extension class: ComboBoxAutoSelectEx really helped a couple of persons. I copied it and it compiles all right. I have to confess though that I have no idea what to do with it. Would you please be so kind as to post a few lines of code in order to exemplify how I may incorporate it into my program and use it in conjunction with comboBox1? Thank you so much for your good will, your effort and your time. — user2102327, Feb 20 '21 at 08:29

Meysam Asadi · Answer 1 · 2021-02-19T12:11:41.523

0

set this code comboBox1.SelectedText = null;

public Form1()
{
    InitializeComponent();
        
   comboBox1 = new ComboBox();
   PopulateComboBox();            
   comboBox1.Location = new Point((this.Width - comboBox1.Width) / 2, 80);            
   this.Controls.Add(comboBox1);

   comboBox1.SelectedText = "A";
   comboBox1.DroppedDown = true;
   comboBox1.SelectedText = null;
}

edited Feb 19 '21 at 12:11

answered Feb 19 '21 at 11:27

Meysam Asadi

6,438
3
7
17

This cannot be correct because the statement: comboBox1.SelectedIndex = 0; specifically selects the first item in the in the Items collection of the ComboBox which is exactly what I want to prevent. – user2102327 Feb 19 '21 at 11:50
You can use comboBox1.SelectedText = "A" – Meysam Asadi Feb 19 '21 at 11:57
The point is for the comboBox1.Text to display the "A". With the statement: comboBox1.SelectedText = "A" ; nothing is displayed! – user2102327 Feb 19 '21 at 12:02
add this code comboBox1.SelectedText = null; I updated the code – Meysam Asadi Feb 19 '21 at 12:05
This does not prevent the automatic selection of the first item and the "A" is not displayed. – user2102327 Feb 19 '21 at 12:11
It works I tested. No items were selected after the control was opened:( – Meysam Asadi Feb 19 '21 at 12:13

score 0 · Answer 2 · answered Feb 20 '21 at 17:49

0

With the help of the thread that Loathing pointed to, I copied the extension Class ComboBoxAutoSelectExtension and in the form I just added the line of code: ComboBoxAutoSelectExtension.AutoSelectOff(comboBox1);

answered Feb 20 '21 at 17:49

user2102327

59
2
6
19

score 0 · Answer 3 · answered Feb 20 '21 at 20:16

If you copy the ComboBoxAutoSelectEx from the link in the comment, then the only thing you should have to do in your own Form1 code is:

public partial class Form1 : Form
{
    public Form1()
    {
        InitializeComponent();
        
        comboBox1 = new ComboBox();

        String text = "A";
        comboBox1.Text = text;
        comboBox1.Select(text.Length,1); // put cursor at the end of text
        ComboBoxAutoSelectEx.AutoSelectOff(comboBox1); // Added

        PopulateComboBox();            
        comboBox1.Location = new Point((this.Width - comboBox1.Width) / 2, 80);            
        this.Controls.Add(comboBox1);

    }

    protected override void OnLoad(EventArgs e) { // Added
        base.OnLoad(e);
        comboBox1.DroppedDown = true;           
    }

    ComboBox comboBox1;

    private void PopulateComboBox()
    {
        comboBox1.Items.Add("Abc");
        comboBox1.Items.Add("Abcd");
        comboBox1.Items.Add("Abcde");
    }

    private void button_Exit_Click(object sender, EventArgs e)
    {
        this.Close();
    }
}

@oathingThank you very much! After some time I found out myself as you can see in the answer I posted myself. — user2102327, Feb 21 '21 at 03:44

Ray Chakrit · Answer 4 · 2023-01-17T22:06:35.783

I see no way to disable auto selection of an item. I can only replace the wrong selection with the input text that was previously known. This bug occurs on both opening or closing the dropdown. Here is an example code when opening the dropdown.

    // record
    box_txt = comboBox1.Text;
    box_pos = comboBox1.SelectionStart;

    // drop down
    comboBox1.DroppedDown = true;

    // replace
    comboBox1.Text = box_txt;
    comboBox1.SelectionStart = box_pos;

How to disable the automatic selection of the first item in ComboBox?

4 Answers4