anchor.diff:    end;
   
   
  +  { TNullableJsonHelper }
  +
  +  TNullableJsonHelper = class
  +  strict private
  +    FList : TStringList;
  +  public
  +    constructor Create;
  +    destructor Destroy; override;
  +
  +    procedure AddValue(const aFieldName: String; const aValue: TAbstractNullable; const aSkipIfNull: boolean);
  +    procedure AddJson(const aJsonString : String);
  +    function GetJson : String;
  +  end;
   
   
   implementation
  
positive.code:     class function VariantToString(const aValue: Variant): String;
  
      function AsString : String; override;
      function AsJson(const aFieldName : String; const aSkipIfNull, aAddComma : boolean): String; override;
  
      property Value : TDateTime read GetValue write SetValue;
    end;
  
negative.code:   end;
  end;
  
  function TNullableDateTime.AsJson(const aFieldName: String; const aSkipIfNull: boolean): String;
  begin
    if Self.IsNull and aSkipIfNull then
      Result := ''
    else
      Result := '"' + aFieldName + '":"' + ISODateTimeToStr(Self.Value) + '"';
  end;
  
  { TAbstractNullable }
  