How to make Combobox in winforms readonly

Question

I do not want the user to be able to change the value displayed in the combobox. I have been using Enabled = false but it grays out the text, so it is not very readable. I want it to behave like a textbox with ReadOnly = true, where the text is displayed normally, but the user can't edit it.

Is there is a way of accomplishing this?

score 175 · Answer 1 · edited Mar 31 '15 at 18:09

175

make DropDownStyle property to DropDownList instead of DropDown then handle the TextChanged event to prevent user changing text.

edited Mar 31 '15 at 18:09

Nam Bình

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answered Feb 21 '09 at 11:29

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Why isn't this the correct answer? Quick, simple and doesn't reinvent the wheel. – DoubleDunk Sep 20 '13 at 17:54
12

This won't prevent the user from selecting different options, only from editing the text. – billpg Sep 25 '13 at 11:38
9

It may not be the correct answer, but for 56 of us (at time of writing,) it was the answer we were looking for (how to disable editing the text.) – Bretticus Jul 07 '14 at 19:08
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I think this solution is better than the accepted one for most of the cases. Thank you! – Ali Ihsan Elmas Nov 09 '20 at 08:07
1

You don't even need to handle the TextChanged event since the user can't change the text. – Robin33 Mar 04 '22 at 09:58
@Bretticus Exactly – David Tejuosho Dec 17 '22 at 02:48

score 23 · Accepted Answer · edited May 08 '13 at 20:27

23

The article ComboBox-with-read-only-behavior suggests an interesting solution:

Create both a readonly textbox and a combobox in the same place. When you want readonly mode, display the textbox, when you want it to be editable, display the combobox.

edited May 08 '13 at 20:27

CodesInChaos

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answered Jan 31 '09 at 05:47

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Downvoted because: This answer is not realy useful. The standard combobox control already provides the desired functionality as @amar vashi pointed out. – Andreas Mar 09 '18 at 19:42
@Andreas - downvote not deserved because this *does* address what the OP wanted; ReadOnly behaviour like the TextBox control, not "limiting user input to items in the list" as most people have assumed. The linked CodeProject article is a more thorough implementation of Niall's answer below. – Rhys Jones May 20 '20 at 21:01

score 11 · Answer 3 · edited Feb 12 '21 at 15:57

11

Not sure if this is what you're looking for but...

Set the DropDownStyle = DropDownList

Then on the SelectedIndexChanged event

if (ComboBox1.SelectedIndex != 0)
{
    ComboBox1.SelectedIndex = 0;
}

This ugly part is that they will "feel" like they can change it. They might think this is an error unless you give them an alert telling them why they can't change the value.

edited Feb 12 '21 at 15:57

ashveli

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answered Dec 24 '08 at 20:42

Dan Williams

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Virus · Answer 4 · 2018-12-19T07:28:12.070

9

enter link description here

Just change the DropDownStyle to DropDownList. Or if you want it completely read only you can set Enabled = false, or if you don't like the look of that I sometimes have two controls, one readonly textbox and one combobox and then hide the combo and show the textbox if it should be completely readonly and vice versa.

edited Dec 19 '18 at 07:28

answered May 11 '15 at 04:18

Virus

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score 9 · Answer 5 · answered Dec 24 '08 at 19:36

The best thing I can suggest is to replace the combo-box with a read-only textbox (or just perhaps a label) - that way the user can still select/copy the value, etc.

Of course, another cheeky tactic would be to set the DropDownStyle to DropDownList, and just remove all other options - then the user has nothing else to pick ;-p

score 5 · Answer 6 · answered Nov 21 '12 at 10:57

I've handled it by subclassing the ComboBox to add a ReadOnly property that hides itself when set and displays a ReadOnly TextBox on top containing the same Text:

class ComboBoxReadOnly : ComboBox
{
    public ComboBoxReadOnly()
    {
        textBox = new TextBox();
        textBox.ReadOnly = true;
        textBox.Visible = false;
    }

    private TextBox textBox;

    private bool readOnly = false;

    public bool ReadOnly
    {
        get { return readOnly; }
        set
        {
            readOnly = value;

            if (readOnly)
            {
                this.Visible = false;
                textBox.Text = this.Text;
                textBox.Location = this.Location;
                textBox.Size = this.Size;
                textBox.Visible = true;

                if (textBox.Parent == null)
                    this.Parent.Controls.Add(textBox);
            }
            else
            {
                this.Visible = true;
                this.textBox.Visible = false;
            }
        }
    }
}

This is a basic version of the CodeProject solution linked in the accepted answer. — Rhys Jones, May 20 '20 at 21:04

score 5 · Answer 7 · edited Sep 15 '11 at 20:07

5

Here is the Best solution for the ReadOnly Combo.

private void combo1_KeyPress(object sender, KeyPressEventArgs e)
{
    e.KeyChar = (char)Keys.None;
}

It will discard the keypress for the Combo.

edited Sep 15 '11 at 20:07

LPL

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answered Sep 10 '10 at 14:09

Manish Parmar

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Nope, doesn't work; that doesn't prevent one from selecting another item from the combobox. – B. Clay Shannon-B. Crow Raven Jul 18 '12 at 17:01
Thanks for this code. It stops users typing custom text into your combo box, allowing them to select whats there but not cause exceptions by inputting their down data. – Dale Woods Dec 08 '16 at 12:32

score 2 · Answer 8 · edited Dec 13 '18 at 22:25

Michael R's code works, but...
The DropDownHeight = 1; must be back to the default value when ReadOnly property is set to false. So, insert before base.OnDropDown(e): DropDownHeight = 106;

using System;
using System.Threading;
using System.Windows.Forms;

namespace Test_Application
{
    class ReadOnlyComboBox : ComboBox
    {
        private bool _readOnly;
        private bool isLoading;
        private bool indexChangedFlag;
        private int lastIndex = -1;
        private string lastText = "";

        public ReadOnlyComboBox()
        {
        }

        public bool ReadOnly
        {
            get { return _readOnly; }
            set { _readOnly = value; }
        }

        protected override void OnDropDown (EventArgs e)
        {
            if (_readOnly)
            {
                DropDownHeight = 1;
                var t = new Thread(CloseDropDown);
                t.Start();
                return;
            }
            DropDownHeight = 106; //Insert this line.
            base.OnDropDown(e);
        }

        private delegate void CloseDropDownDelegate();
        private void WaitForDropDown()
        {
            if (InvokeRequired)
            {
                var d = new CloseDropDownDelegate (WaitForDropDown);
                Invoke(d);
            }
            else
            {
                DroppedDown = false;
            }
        }
        private void CloseDropDown()
        {
            WaitForDropDown();
        }

        protected override void OnMouseWheel (MouseEventArgs e)
        {
            if (!_readOnly) 
                base.OnMouseWheel(e);
        }

        protected override void OnKeyDown (KeyEventArgs e)
        {
            if (_readOnly)
            {
                switch (e.KeyCode)
                {
                    case Keys.Back:
                    case Keys.Delete:
                    case Keys.Up:
                    case Keys.Down:
                        e.SuppressKeyPress = true;
                        return;
                }
            }
            base.OnKeyDown(e);
        }

        protected override void OnKeyPress (KeyPressEventArgs e)
        {
            if (_readOnly)
            {
                e.Handled = true;
                return;
            }
            base.OnKeyPress(e);
        }
    }
}

To complete this answer:

File -> New -> Project... Visual C# -> Windows -> Classic Desktop -> Windows Forms Control Library

type the Name of your control - OK and paste this code.

You can choose the name of your dll file:
Project - yourproject Properties...

Assembly name: type the name. Just build the solution and you have your dll file. So, open the project where you want to use your Read Only combo, right click on References
Add Reference... and browse your dll file. To Insert your custom component into Toolbox, open your Toolbox, right click on General tab -> Choose Items...
Browse your dll file - Open. Now you can use your ReadOnlyComboBox in your projects. PS: I'm using VS2015.

score 1 · Answer 9 · answered Oct 20 '12 at 12:33

1

This is how you would address the fact that a ComboBox with Enabled = False is hard to read:

A combobox that looks decent when it is disabled

answered Oct 20 '12 at 12:33

Victor Zakharov

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score 1 · Answer 10 · edited May 08 '13 at 20:34

1

Actually, its rather simple:

Private Sub combobox1_KeyDown(ByVal sender As Object, ByVal e As System.Windows.Forms.KeyEventArgs) Handles combobox1.KeyDown
    ' the following makes this the combobox read only    
    e.SuppressKeyPress = True    
End Sub

edited May 08 '13 at 20:34

CodesInChaos

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answered Nov 27 '09 at 02:24

Rob

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Simple, but doesn't work. That doesn't prevent one from selecting another item from the combobox. – B. Clay Shannon-B. Crow Raven Jul 18 '12 at 16:59

score 1 · Answer 11 · answered Dec 24 '08 at 21:11

1

You can change the forecolor and backcolor to the system colors for an enabled combo box, although this may confuse the users (why have it if they can't change it), it will look better.

answered Dec 24 '08 at 21:11

Tom Anderson

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Nalaka526 · Answer 12 · 2014-07-04T09:47:18.117

0

Set DropdownStyle Property to Simple

Add below code to to KeyPress event of ComboBox

private void comboBoxName_KeyPress(object sender, KeyPressEventArgs e)
{
    e.Handled = true;
    return;
}

Add below code to to KeyDown event of ComboBox

private void comboBoxName_KeyDown(object sender, KeyEventArgs e)
{
    e.Handled = true;
    return;
}

edited Jul 04 '14 at 09:47

answered Jul 04 '14 at 09:34

Nalaka526

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score 0 · Answer 13 · answered Aug 16 '14 at 01:07

If you've already populated it, and selected the appropriate item, and made it a DropDownList, then you can use an extension method like this to quickly reduce the selection list down to just the selected item:

public static void MakeReadOnly(this ComboBox pComboBox) {
   if (pComboBox.SelectedItem == null)
      return;

   pComboBox.DataSource = new List<object> {
      pComboBox.SelectedItem
   };
}

score 0 · Answer 14 · answered Dec 04 '14 at 06:28

I know that I'm a little late to the party, but I was researching this exact question and I knew that there had to be some way to make the combobox readonly as if it were a textbox and disabled the list popping up. It's not perfect, but it is definitely better than all of the answers I've been finding all over the internet that don't work for me. After the button is pressed and the OnDropDown is called, a new thread is created that will set the DroppedDown property to false, thus creating the effect of "nothing happening." The mouse wheel is consumed and key events are consumed as well.

using System;
using System.Threading;
using System.Windows.Forms;

namespace Test_Application
{
    class ReadOnlyComboBox : ComboBox
    {
        private bool _readOnly;
        private bool isLoading;
        private bool indexChangedFlag;
        private int lastIndex = -1;
        private string lastText = "";

        public ReadOnlyComboBox()
        {
        }

        public bool ReadOnly
        {
            get { return _readOnly; }
            set { _readOnly = value; }
        }

        protected override void OnDropDown(EventArgs e)
        {
            if (_readOnly)
            {
                DropDownHeight = 1;
                var t = new Thread(CloseDropDown);
                t.Start();
                return;
            }
            base.OnDropDown(e);
        }

        private delegate void CloseDropDownDelegate();
        private void WaitForDropDown()
        {
            if (InvokeRequired)
            {
                var d = new CloseDropDownDelegate(WaitForDropDown);
                Invoke(d);
            }
            else
            {
                DroppedDown = false;
            }
        }
        private void CloseDropDown()
        {
            WaitForDropDown();
        }

        protected override void OnMouseWheel(MouseEventArgs e)
        {
            if (!_readOnly) 
                base.OnMouseWheel(e);
        }

        protected override void OnKeyDown(KeyEventArgs e)
        {
            if (_readOnly)
            {
                switch (e.KeyCode)
                {
                    case Keys.Back:
                    case Keys.Delete:
                    case Keys.Up:
                    case Keys.Down:
                        e.SuppressKeyPress = true;
                        return;
                }
            }
            base.OnKeyDown(e);
        }

        protected override void OnKeyPress(KeyPressEventArgs e)
        {
            if (_readOnly)
            {
                e.Handled = true;
                return;
            }
            base.OnKeyPress(e);
        }
    }
}

snir · Answer 15 · 2016-01-19T09:52:17.687

0

Simplest way in code:

instead of adding methods for KeyPress or KeyDown, add this code on 'Form1_Load' method:

comboBox1.KeyPress += (sndr, eva) => eva.Handled = true;

or

comboBox1.KeyDown += (sndr, eva) => eva.SuppressKeyPress = true;

(sndr, eva) is for (object sender, EventArgs e)

edited Jan 19 '16 at 09:52

answered Jan 19 '16 at 09:45

snir

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score 0 · Answer 16 · answered Feb 21 '09 at 12:29

Why don't you just use a text box? Text box has a "Read only" property, and since you want your combo box only to display data, I don't see why you would need a combo box.

An alternative is that you just cancel out the input for the "on value changed" event. That way you will be displaying your information no mater what user does ...

score 0 · Answer 17 · answered May 17 '20 at 21:14

I dont know if that is what you are looking but this prevents the user from chosing any item from the drop down and still be able to type text in the combobox. If you dont want the user to type text in the combobox you can make it Dropdown list from the properties menu.

So you get Read Only combobox.

On Selected Index Changed

Make the selected Index -1 "comboBox.SelectedIndex = -1";

    private void MyComboBox_comboBox_SelectedIndexChanged(object sender, EventArgs e)
    {
        MyComboBox_comboBox.SelectedIndex = -1; 

    }

score -1 · Answer 18 · edited Nov 12 '11 at 17:01

-1

Here is the Best solution for the ReadOnly Combo.

private void combo1_KeyPress(object sender, KeyPressEventArgs e) {
    e.KeyChar = (char)Keys.None; 
}

It will discard the keypress for the Combo. It doesn't have "e.KeyChar" !

edited Nov 12 '11 at 17:01

NullUserException

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answered Nov 12 '11 at 16:59

Behzad

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Why does this look almost exactly like the Manish answer? What does "it doesn't have e.KeyChar" mean? – LarsTech Nov 12 '11 at 17:10
Oops! You're right! I was wrong, I used KeyDown event instead of KeyPress event. Sorry! – Behzad Nov 16 '11 at 17:42

How to make Combobox in winforms readonly

18 Answers18

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