How to make Combobox in winforms readonly

Question

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

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.

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.

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

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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.

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;
            }
        }
    }
}