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   type
2     TForm = class(TForm)
3       {....... }
4     private
5       FSearchStr: string;
6     end;


2. Add initialisation of this string variable in Form's OnCreate event: 

FSearchStr := '';

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


Now you'll see how it will work.