动态创建字段代码不能用，提示“序号”找不到，请高人指点！(50分)

给网上找的创建字段的代码，却不能用，提示创建的字段找不到，
procedure TForm1.Button1Click(Sender: TObject);
var
T:TStringField;
begin
Adoquery1.Close;
T:=TStringField.Create(ADOQuery1);
T.FieldName:='序号';
T.Index:=Adoquery1.FieldCount;
T.DataSet:=Adoquery1;
T:=TStringField.Create(ADOQuery1);
T.FieldName:='姓名';
T.Index:=Adoquery1.FieldCount;
T.DataSet:=Adoquery1;
Adoquery1.FieldDefs.Update;
Adoquery1.Open;
end;

procedure AddField(AFieldType: TFieldType;AName: string;ASize: Integer);
begin
with DataSet do
with FieldDefs.AddFieldDef do
begin
DataType := AFieldType;
Size := ASize;
Name := AName;
end;
end;

...

...
AddField(ftString,'姓名',16);