How to make Combobox in winforms readonly

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

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.

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 ...

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.

1. On Selected Index Changed

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

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