ComboBox dropdown flickering in windows application C#.net 2005

[Vidhura]

My application contains 2 tabpages.The second tabpage contains panel .The panel contains series of combobox and textboxes.

If the item not selected in combobox and the user click on the another tabpage,it should show "The option from dropdown should be selected" and focus the combo .I have did this in validating event

void cmbDistributionOption_Validating(object sender, CancelEventArgs e)
{
ComboBox cmb = (ComboBox)sender;
if (cmb.SelectedIndex <= 0)
{
MessageBox.Show("The option from dropdown should be selected.", "Popup", MessageBoxButtons.OK);
e.Cancel = true;



}
}

it works fine till focusing the combo.If I again try to select the combo which is focused,the dropdown of the combo is flickering(dropdown shows and goes up)
I tried to select the item but its not possible.

Any solution for this weird behaviour?

[Vidhura]

My application contains 2 tabpages.The second tabpage contains panel .The panel contains series of combobox and textboxes.

If the item not selected in combobox and the user click on the another tabpage,it should show "The option from dropdown should be selected" and focus the combo .I have did this in validating event



it works fine till focusing the combo.If I again try to select the combo which is focused,the dropdown of the combo is flickering(dropdown shows and goes up)
I tried to select the item but its not possible.

Any solution for this weird behaviour?

plz Anyone help me on this?

[Vidhura]

Finally I have found the solution for this issue.

May be it help someone,so I m posting the solution for this

Issue:

My application contains 2 tabpages.The second tabpage contains panel .
The panel contains series of combobox and textboxes.
If the item not selected in combobox and the user click on the another tabpage,
it should show "The option from dropdown should be selected" and focus the combo .

I have did this using e.cancel= true in combobox_validating event (which have been wrong)
it works fine till focusing the combo.If I again try to select the combo which is focused,the dropdown of the combo is flickering(dropdown shows and goes up)
I tried to select the item but its not possible.


Solution:

When you need this kind of functionality in tabpages please dont put it in controls validating event.
because after all this, the controls events are not firing(Mouse events,click events)


Instead set value to the variable,and do the e.cancel= true in tabcontrol_selecting event.

public  bool cancel = false;
 
 void Combobox_Validating(object sender, CancelEventArgs e)
 {     
 
           if (Combox.selectedindex <=0 )
            {
               MessageBox.Show("This is required field. Please enter value(s).", "Popup", MessageBoxButtons.OK);     
               cancel = true;
             }
            else
            {               
               cancel = false;
            }
 
 }
 
 
 
 void tabCtrl_Selecting(object sender, System.Windows.Forms.TabControlCancelEventArgs e)
 {
         if (cancel == true)
         {
            e.Cancel = true;
         }
 }