Question

How can I remove duplicate items from ListBox in Delphi? I know this:

for i := ListBox1.Items.Count-1 downto 1 do
     for j := 0 to i-1 do
       if ListBox1.Items[i] = ListBox1.Items[j] then
         ListBox1.Items.Delete[i]; 

But I need to remove duplicates only if first 10 letters are the same, so I have tried this:

for i := ListBox1.Items.Count-1 downto 1 do
         for j := 0 to i-1 do
           if copy(ListBox1.Items[i],1,11) = copy(ListBox1.Items[j],1,11) then
             ListBox1.Items.Delete[i]; 

But when I try to remove duplicates, I get list out of bonds error 🙁

Answer 1

You need to add a break after the Delete:

if Copy(ListBox1.Items[i], 1, 10) = Copy(ListBox1.Items[j], 1, 10) then
begin
  ListBox1.Items.Delete(i); 
  break;
end;

(Indeed, if you Delete the item with index i, then how can you make the comparison if Copy(ListBox1.Items[i], 1, 10) = ... the next time?)