Как удалить выбранную в поле редактирования строку из списка TComboBox

unit U5_1;
 
interface
 
uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs, Buttons, StdCtrls;
 
type
  TForm1 = class(TForm)
    Memo1: TMemo;
    ComboBox1: TComboBox;
    ListBox1: TListBox;
    Button1: TButton;
    Button2: TButton;
    Button3: TButton;
    Button4: TButton;
    Button5: TButton;
    Button6: TButton;
    Button7: TButton;
    BitBtn1: TBitBtn;
    BitBtn2: TBitBtn;
    BitBtn3: TBitBtn;
    BitBtn4: TBitBtn;
    BitBtn5: TBitBtn;
    BitBtn6: TBitBtn;
    procedure Button1Click(Sender: TObject);
    procedure Button6Click(Sender: TObject);
    procedure Button2Click(Sender: TObject);
    procedure Button3Click(Sender: TObject);
    procedure Button4Click(Sender: TObject);
    procedure Button5Click(Sender: TObject);
    procedure Button7Click(Sender: TObject);
    procedure BitBtn1Click(Sender: TObject);
    procedure BitBtn4Click(Sender: TObject);
    procedure BitBtn2Click(Sender: TObject);
    procedure BitBtn5Click(Sender: TObject);
    procedure BitBtn6Click(Sender: TObject);
    procedure BitBtn3Click(Sender: TObject);
 
 
    
 
  private
    { Private declarations }
  public
    { Public declarations }
  end;
 
var
  Form1: TForm1;
  i:integer;
implementation
 
{$R *.dfm}
 
 
 
 
 
procedure TForm1.BitBtn1Click(Sender: TObject);
begin
  Memo1.ClearSelection;
end;
 
procedure TForm1.BitBtn2Click(Sender: TObject);
begin
 
end;
 
procedure TForm1.BitBtn3Click(Sender: TObject);
begin
 
end;
 
procedure TForm1.BitBtn4Click(Sender: TObject);
begin
Memo1.Lines.Clear;
end;
 
procedure TForm1.BitBtn5Click(Sender: TObject);
begin
 
end;
 
procedure TForm1.BitBtn6Click(Sender: TObject);
begin
 
end;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
for i:=0 to Memo1.Lines.Count-1 do
ComboBox1.AddItem(Memo1.Lines[i],ComboBox1);
end;
 
procedure TForm1.Button2Click(Sender: TObject);
begin
for i := 0 to Memo1.Lines.Count - 1 do
ComboBox1.AddItem(ListBox1);
 
end;
 
procedure TForm1.Button3Click(Sender: TObject);
begin
for i := 0 to ComboBox1.Items.Count - 1 do
ComboBox1.AddItem(ListBox1);
end;
 
procedure TForm1.Button4Click(Sender: TObject);
begin
for i := 0 to ComboBox1.Items.Count - 1 do
Memo1.Lines.Add(ComboBox1);
end;
 
procedure TForm1.Button5Click(Sender: TObject);
begin
for i:=0 to ListBox1.Items.Count-1 do
Memo1.Lines.Add(ListBox1);
end;
 
procedure TForm1.Button6Click(Sender: TObject);
begin
for i:=0 to ListBox1.Items.Count-1 do
       ComboBox1.AddItem(ListBox1.Items[i],ComboBox1);
end;
 
 
 
procedure TForm1.Button7Click(Sender: TObject);
begin
ComboBox1.Items.Add(ComboBox1.Text);
end;
 
end.

procedure TForm1.ComboBox1Change(Sender: TObject);
begin
ComboBox1.Items.Delete(ComboBox1.ItemIndex);
end;
 
procedure TForm1.Button1Click(Sender: TObject);
begin
ComboBox1.Clear
end;
 
procedure TForm1.ListBox1Click(Sender: TObject);
begin
ListBox1.Items.Delete(ListBox1.ItemIndex);
end;
 
procedure TForm1.Button2Click(Sender: TObject);
begin
ListBox1.Clear
end;

if Combobox1.Items.IndexOf(Combobox1.Text) < 0 then
  Combobox1.Items.Add(Combobox1.Text);