Author: Igor Siticov

How to realise automatic search feature in ComboBox?

Answer:

For including this functionality we shall just handle KeyPress event of ListBox or 
ComboBox. 
Below is demonstartion of this realisation: 

1. Add string variable to your form: 
1   
2   type
3     TForm = class(TForm)
4       {....... }
5     private
6       FSearchStr: string;
7     end;
8   
9   //2.Add initialisation of this string variable in Form's OnCreate event: 
10  
11  FSearchStr := '';
12  
13  //3.Type the following code in OnKeyPress event of ListBox or ComboBox: 
14  
15  procedure TForm1.ListBox1KeyPress(Sender: TObject; var Key: Char);
16  var
17    i: Integer;
18  begin
19    case Key of
20      #27:
21        begin
22          // Escape key, clear search string
23          FSearchStr := EmptyStr;
24        end; { Case Esc }
25      #8:
26        begin
27          // backspace, erase last key from search string
28          if Length(FSearchStr) > 0 then
29            Delete(FSearchStr, Length(FSearchStr), 1);
30        end; { Case backspace }
31    else
32      FSearchStr := FSearchStr + Key;
33    end; { Case }
34    if Length(FSearchStr) > 0 then
35      if Sender is TListbox then
36      begin
37        i := SendMessage(TListbox(Sender).handle, LB_FINDSTRING,
38          TListbox(Sender).ItemIndex, longint(@FSearchStr[1]));
39        if i <> LB_ERR then
40          TListbox(Sender).ItemIndex := i;
41      end
42      else if Sender is TCombobox then
43      begin
44        i := SendMessage(TCombobox(Sender).handle, CB_FINDSTRING,
45          TCombobox(Sender).ItemIndex, longint(@FSearchStr[1]));
46        if i <> LB_ERR then
47          TCombobox(Sender).ItemIndex := i;
48      end;
49    Key := #0;
50  end;


Now you'll see how it will work.