How can I handle ComboBox selected index changing?

Question

I have a ComboBox that have a list of manufacturers. When a user selects a manufacturer, a grid below is populated with data for the chosen manufacturer. That data can be mo

Answer 1

Night Coder's solution is elegant and concise. I have packaged it in a dll.
(I call it CustomControls.) To do this create a new class library and add the first few statements to Night Coder's solution (copied here as a convenience).

Once you have compiled the code, you can add it as a reference. I actually loaded the dll into my Visual Studio Tools pane. That way I can drag the control onto my form at design time. Conveniently, the new event shows up in the properties list.

use System.ComponentModel;

use System.Windows.Forms; //this will need to be added as a reference

//your namespace will name your dll call it what you will

namespace CustomControls

Night Coder's solution follows:

public class ComboBoxEx : ComboBox
{
        public event CancelEventHandler SelectedIndexChanging;


    [Browsable(false)]
    public int LastAcceptedSelectedIndex { get; private set; }

    public ComboBoxEx()
    {
            LastAcceptedSelectedIndex = -1;
    }

    protected void OnSelectedIndexChanging(CancelEventArgs e)
    {
            var selectedIndexChanging = SelectedIndexChanging;
            if (selectedIndexChanging != null)
                    selectedIndexChanging(this, e);
    }


    protected override void OnSelectedIndexChanged(EventArgs e)
    {
            if (LastAcceptedSelectedIndex != SelectedIndex)
            {
                    var cancelEventArgs = new CancelEventArgs();
                    OnSelectedIndexChanging(cancelEventArgs);

                    if (!cancelEventArgs.Cancel)
                    {
                            LastAcceptedSelectedIndex = SelectedIndex;
                            base.OnSelectedIndexChanged(e);
                    }
                    else
                            SelectedIndex = LastAcceptedSelectedIndex;
            }
    }
}