SelectedIndexChanging Event? in UI for WinForms

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SelectedIndexChanging Event?

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ComboBox and ListBox (obsolete as of Q2 2010)

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answered on 24 Sep 2010, 04:46 PM

I was able to extend the radcombobox so that the selectedindexchanging event fires that allows the developer to cancel the selectedindexchanged event.
This will be useful for developers using Telerik RadControls for Winforms version prior to 2010 Q2.
The attached project contains an extended custom control that inherits RadComboBox but adds new functionality of selectedindexchanging event.

The complete code for such a custom control is given below.

using System;

using System.Collections.Generic;

using System.ComponentModel;

using System.Data;

using System.Drawing;

using System.Linq;

using System.Text;

using System.Windows.Forms;

using Telerik.WinControls.UI;

using Telerik.WinControls;

namespace MyControls

{

public partial class RadComboBoxPlus : RadComboBox

{

public event CancelEventHandler SelectedIndexChanging;

[Browsable(false)]

public int PreviousSelectedIndex { get; private set; }

public RadComboBoxPlus()

{

InitializeComponent();

PreviousSelectedIndex = -1;

}

public override string ThemeClassName

{

get

{

return typeof(RadComboBox).FullName;

}

protected void OnSelectedIndexChanging(CancelEventArgs e)

{

var selectedIndexChanging = SelectedIndexChanging;

if (selectedIndexChanging != null)

selectedIndexChanging(this, e);

}

protected override void OnSelectedIndexChanged(EventArgs e)

{

if (PreviousSelectedIndex != SelectedIndex)

{

var cancelEventArgs = new CancelEventArgs();

OnSelectedIndexChanging(cancelEventArgs);

if (!cancelEventArgs.Cancel)

{

PreviousSelectedIndex = SelectedIndex;

base.OnSelectedIndexChanged(e);

}

else

SelectedIndex = PreviousSelectedIndex;

}

protected override void OnPaint(PaintEventArgs pe)

{

base.OnPaint(pe);

}