Incompatible types: 'String' and 'TStringList'

Question

[Error] Unit1.pas(39): Incompatible types: 'String' and 'TStringList'我是想把'TStringList'类型的值赋给'String'出现上面的错误任何解决呢

Answer 1

procedure TForm1.Button1Click(Sender: TObject);
var
Sa:Tstrings;
Sb:TstringList;
begin
      Sb:=TstringList.Create;
      sa:=(sb as Tstrings);
      Sb.Free;end;

Answer 2

是不是字符串类型的值？procedure TForm1.Button1Click(Sender: TObject);
var
Sa:String;
Sb:TstringList;
begin
      Sb:=TstringList.Create;
      sa:=Sb.text;
      Sb.Free;end;

Answer 3

procedure TForm1.Button1Click(Sender: TObject);
var
Sa:Tstrings;
Sb:TstringList;
begin
      Sa:=TstringList.Create;
end;
//这样不行吗？
多态啊？