anchor.diff:    else
       SetValue(VarToStr(aValue));
   end;
  -
  -procedure TNullableStringRecord.Assign(const aValue: String; const aAllowBlankValue: boolean);
  -begin
  -  Self.Assign(aValue);
  -  if aAllowBlankValue then
  -    Self.ChangeToBlankIfNull;
  -end;
  -
   
   function TNullableStringRecord.AsVariant: Variant;
   begin
  
positive.code:     Self.Value:= '';
  end;
  
  class function TNullableString.StringToVariant(const aValue: String): Variant;
  begin
    if aValue = '' then
      Result:= Null
    else
      Result:= aValue;
  
negative.code:     constructor Create(aValue: Boolean); overload;
  
      procedure Assign(const aSource : TNullableBoolean); overload;
      procedure Assign(const aSourceField : TField); overload;
      procedure Assign(const aSourceField: TField; const aAllowNull: boolean); overload;
      procedure Assign (const aValue : Variant); override; overload;
      procedure Assign (const aValue : string); overload;
  
      function CheckIfDifferentAndAssign(const aValue : Variant) : boolean; override;
      function AsVariant: Variant; override;
  