combobox prevent index change

you can use customvalidator and a hiddenfield to do this.

I think you should not validate this at indexchange because it will irritate the user. You should check it at the time of submit of the page.

Sorry this is windows not asp.

here is a sample code
======================


Dim s As Integer

Dim changed As Boolean = False

Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged

        If Not changed Then

            If Not (MessageBox.Show("Are u sure", "Confirm", MessageBoxButtons.YesNo, MessageBoxIcon.Question) = Windows.Forms.DialogResult.Yes) Then

                changed = True

                ComboBox1.SelectedIndex = s

            End If

        End If

        changed = True

    End Sub

    Private Sub ComboBox1_DropDown(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ComboBox1.DropDown

        s = ComboBox1.SelectedIndex

        changed = False

    End Sub

KS:

The static variable will work for you in that case.

static int oldIndex = null;

if (oldIndex != null)
{
   if(displayAlert()) //save new selection
     oldindex = combobox1.SelectedIndex;
   else  //revert back
     ComboBox1.SelectedIndex = oldindex;
}
else  // handles first time through, just save index as old index
   oldIndex = ComboBox1.SelectedIndex;

There is no "changed" event in windows and as I said in my original post I have the code in the drop down but that will not catch when users use the mouse scroll or arrow keys.

The best method is to inherit ComboBox in a new class and override 'OnSelectedIndexChanged' method in which you have complete control...
An inherited class is available here => http://stackoverflow.com/questions/782313/how-can-i-handle-combobox-selected-index-changing

OR if this is too much for your code, then you can still use the SelectedIndexChanged event as shown in the code below..

// _canceling variable is used to prevent the messagebox again display when we set the value back to the previous value.

private int _currentIndex = -1;
        private bool _canceling = false;

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (!_canceling)
            {
                DialogResult res = MessageBox.Show(this, "Want to change?", "", MessageBoxButtons.YesNo);
                if (res == DialogResult.No)
                {
                    
                        try
                        {
                            _canceling = true;

                            comboBox1.SelectedIndex = _currentIndex;
                        }
                        finally
                        {
                            _canceling = false;
                        }
                    
                }
            }

            _currentIndex = comboBox1.SelectedIndex;
        }

Select allOpen in new window

try this as well:

You can notify user on this event as well:
comboBox1_SelectedValueChanged

This event fires before comboBox1_SelectedIndexChanged event

int index = 0; Boolean ShowMessage=true; 
         private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)
        {
            if (ShowMessage)
            {
                if (MessageBox.Show("Are you sure to change selection?", "Notification", MessageBoxButtons.OKCancel, MessageBoxIcon.Question) == DialogResult.OK)
                    return;
                ShowMessage = false; comboBox1.SelectedItem = comboBox1.Items[index]; 
            }
        }

        private void comboBox1_MouseEnter(object sender, EventArgs e)
        {
            index = comboBox1.SelectedIndex; ShowMessage=true;
        }

Select allOpen in new window

There is another event handler:

private void YourComboBox_MouseWheel(object sender, MouseEventArgs e)

you can call make your own function, then point to that function to the alert.

Another way to do this is to disable the control, with a button to unlock it.  Then put the confirmation in the click event.

Thank you for the suggestions, but I don't see a MouseWheel event.

What .Net Version?

Also it looks like you can create your own to inherit it:
http://stackoverflow.com/questions/2968189/disable-mouse-scroll-wheel-in-combobox-vb-net

Hello KS_Mis,

Are the above comments useful. We would be happy to help you further if you need...

Thanks