TComboBox and TListBox item Removal?

Question

i am trying to add items to TListBox and TComboBox from text given in TEdit My code is working fine while adding item in TListBox TComboBox but when i try to remove the selected item in TListBox from itself and from TComobBox it shows Access Violation.

Below is procedure from my code:-

procedure TMainForm.Button1Click(Sender: TObject);
begin
  ListBox1.Items.Add(Edit1.Text);   
  ComboBox1.Items.Add(Edit1.Text);
end;

procedure TMainForm.Button2Click(Sender: TObject);
begin
  ListBox1.Items.Delete(ListBox1.Selected.Index);
  ComboBox1.Items.Delete(ComboBox1.Items.IndexOf(ListBox1.Selected.Text));
end;

Solved: Did a Kiddish Mistake now Solved. Here it is working code:

procedure TMainForm.Button2Click(Sender: TObject);
begin
  ComboBox1.Items.Delete(ComboBox1.Items.IndexOf(ListBox1.Selected.Text));
  ListBox1.Items.Delete(ListBox1.Selected.Index);      
end;

Answer 1

A safe(r) way to do the deletions is

procedure TForm1.DeleteItems(const TextToFind : String);
var
  i1,
  i2 : Integer;
begin
  i1 := ListBox1.Items.IndexOf(TextToFind);  
  i2 := ComboBox1.Items.IndexOf(TextToFind);
  if i1 >=0 then
    ListBox1.Items.Delete(i1);
  if i2 >=0 then
    ComboBox1.Items.Delete(i2);
end;

Usage:

DeleteItems(Edit1.Text);

because this does not make assumptions about which items are selected in the two lists.

I leave you to find out using the debugger why you are getting the AV. It will be more instructive for you to find out than me to tell you.

Answer 2

This line removes the item from the listbox

ListBox1.Items.Delete(ListBox1.Selected.Index);

This line is trying to remove the item from the combobox

ComboBox1.Items.Delete(ComboBox1.Items.IndexOf(ListBox1.Selected.Text));

But in it you refer to ListBox1.Selected.Text. This is referring the item you just removed in the first delete. Swapping the order of execution around should work:

begin
  ComboBox1.Items.Delete(ComboBox1.Items.IndexOf(ListBox1.Selected.Text));
  ListBox1.Items.Delete(ListBox1.Selected.Index);
end