Question

How to select all text of a TEdit1 whenever user click on it or click to select some text of it

Answer 1

How to select all text of a TEdit1 whenever user click on it

Select Edit1 in the VCL editor and double-click on the OnClick event:

procedure TForm13.Edit1Click(Sender: TObject);
begin
  Edit1.SelectAll;
end;

You can also link this event to another control like a button.
Select the button, choose and click on the V arrow to select an event you want to link.

Now both Edit1.OnClick and Button1.OnClick link to the same event.