anchor.diff:      Result := FValue;
   end;
   
  -function TNullableDateTime.ToString(aShowTime: boolean): String;
  +function TNullableDateTime.AsString(aShowTime: boolean): String;
   begin
     if Self.IsNull then
       Result := ''
  
positive.code:     Result := FValue;
  end;
  
  function TNullableInteger.ToString: String;
  begin
    if Self.IsNull then
      Result := ''
  
negative.code:       procedure Assign(aSourceField : TField); overload;
        function AsVariant: Variant; override;
  
        function AsString (aShowTime : boolean) : String;
  
        property Value : TDateTime read GetValue write SetValue;
    end;
  