Restricting User Typing in RadAutoCompleteBox

Updated on Aug 11, 2025

Environment

Product Version	Product	Author
2025.2.520	RadAutoCompleteBox for WinForms	Dinko Krastev

Description

In the following scenario, we will demonstrate how to prevent the end user from typing in the control. The user should interact with the control only by clicking an external button (e.g., Attach), which opens a file dialog for selecting files to attach.

Solution

To disable user input in the RadAutoCompleteBox, you can override its KeyDown method by customizing the RadAutoCompleteBoxElement. Follow these steps:

1. Create a custom class that inherits from RadAutoCompleteBox.
2. Override the CreateTextBoxElement method to return the custom RadAutoCompleteBoxElement.
3. Inside the custom RadAutoCompleteBoxElement, override the OnKeyDown method to suppress key presses.

Here is the code implementation:

C#

public class MyAutoCompleteBoxControl : RadAutoCompleteBox
{
    public override string ThemeClassName
    {
        get
        {
            return typeof(RadAutoCompleteBox).FullName;
        }
    }
    protected override RadTextBoxControlElement CreateTextBoxElement()
    {
        return new MyAutoCompleteBoxElement();
    }
}

public class MyAutoCompleteBoxElement : RadAutoCompleteBoxElement
{
    protected override Type ThemeEffectiveType
    {
        get
        {
            return typeof(RadAutoCompleteBoxElement);
        }
    }
    protected override void OnKeyDown(KeyEventArgs e)
    {
        e.SuppressKeyPress = true;
        e.Handled = true;
    }
}

Replace the standard RadAutoCompleteBox with the custom MyAutoCompleteBoxControl in your application. This will prevent users from typing in the control.

See Also

• RadAutoCompleteBox Documentation