List box object reference error

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Hi All,

I have 2 list boxes lbabcList, lbxyzList and when I select the item from lbabcList box and click on the addbutton then it should go to lbxyzList box.

I am ending up with 'object reference not set to instance of object' error when I don`t select any item from the lbabcList box and click on addbutton.

How to solve this error

Here is my code in the addbutton_click.

Add the selected item to the event groups list

VB

lbxyzList.Items.Add(lbabcList.SelectedItem)

remove the event from the master list of events

VB

lbabcList.Items.Remove(lbabcList.SelectedItem)

lbxyzList.ClearSelection()

Thanks,
YesP

Posted 28-Aug-12 9:11am

YesPriya

Updated 28-Aug-12 10:59am

RaisKazi

v2

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Christian Amado · Answer 1 · 2012-08-28T09:20:00

C#

if (lbabcList.SelectedItem != null){
    //add the selected item to the event groups list
    lbxyzList.Items.Add(lbabcList.SelectedItem)
 
    //remove the event from the master list of events
    lbabcList.Items.Remove(lbabcList.SelectedItem)
 
    lbxyzList.ClearSelection()
}
else{
   //Show a message if the user not selected an item
}

Hope it helps

**Zoltán Zörgő** · Answer 2 · 2012-08-28T09:24:00

Solution 3

You answered on your own! If nothing is selected , .SelectedItem will be null. Check it before trying to add. Or use the SelectedItemChanged[^] event to disable button if nothing is selected. If multiple selection is allowed, use SelectedItems[^] collection instead.

Posted 28-Aug-12 9:24am

Zoltán Zörgő

Sandip.Nascar · Answer 3 · 2012-08-28T09:24:00

You need to check the item is null or not.
When you are not selecting anything in left listbox, the selected item is null and you are trying to add null object in right list box

Check the code here,

if(lbabcList..SelectedIndex >= 0){ //i.e not -1
  //do your add/remove stuff
}

OR

if(lbabcList.SelectedItem!=null){
   // do your add stuff
}

Hope this solves.
cheers

List box object reference error

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