anchor.diff:  begin
     if not Self.IsNull then
       Self.Value:= SysUtils.Trim(Self.Value);
  +end;
  +
  +procedure TNullableString.ChangeToBlankIfNull;
  +begin
  +  if Self.IsNull then
  +    Self.Value:= '';
   end;
   
   class function TNullableString.StringToVariant(const aValue: String): Variant;
  
positive.code: 
  {$IFDEF FPC}
    {$MODE DELPHI}
  {$ENDIF}
  
  interface
  
negative.code:     procedure Assign(aSourceField : TField); override; overload;
      procedure Assign(const aValue : String); override; overload;
      procedure Assign(const aValue : Variant); override; overload;
      procedure Assign(const  aValue : String; const aAllowBlankValue : boolean); overload;
      function CheckIfDifferentAndAssign(const aValue : Variant) : boolean;
      function AsVariant: Variant; override;
      procedure Trim();
      procedure ChangeToBlankIfNull;
  
      class function StringToVariant(const aValue : String) : Variant;
  
  