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