anchor.diff:      Self.Value := aSource.Value
     else
       Self.IsNull := true;
  +  FTagChanged:= false;
   end;
   
   procedure TNullableBoolean.Assign(aSourceField: TField);
  
positive.code:     class function StringToVariant(const aValue: String): Variant;
      class function VariantToString(const aValue: Variant; const aDigits : byte): String;
  
      function CheckIfDifferentAndAssign(const aValue : Variant) : boolean;
  
      function AsString : String;
      function AsFloat : Double;
  
negative.code:     Self.Value := aSource.Value
    else
      Self.IsNull := true;
    FTagChanged:= false;
  end;
  
  procedure TNullableInteger.Assign(aSourceField: TField);
  