Delphi Invalid Class Typecast - delphi

Question

I'm trying to build an Delphi class for Invoice, and invoice Lines Array,to export it to JSON , I went to JSONTODelphi.com and I extract the class and add it to my project, but i each time i want to assign a value to (Partner_Shipping_Id) in the class I got "Invalid Class typecast" here my code :
unit Quotation;
interface
uses Pkg.Json.DTO, System.Generics.Collections, REST.Json.Types;
{$M+}
type
TQuotationLines = class
private
FDiscount: Integer;
FPrice: Double;
FProduct_Id: Integer;
FQuantity: Integer;
FTax_Id: Integer;
published
property Discount: Integer read FDiscount write FDiscount;
property Price: Double read FPrice write FPrice;
property Product_Id: Integer read FProduct_Id write FProduct_Id;
property Quantity: Integer read FQuantity write FQuantity;
property Tax_Id: Integer read FTax_Id write FTax_Id;
end;
TQuotationInvoice = class(TJsonDTO)
private
FCash_Van_Id: Integer;
FData: TDate;
FPartner_Id: Integer;
FPartner_Invoice_Id: Integer;
FPartner_Shipping_Id: Integer;
FPricelist_Id: Integer;
[GenericListReflect]
FLines: TObjectList<TQuotationLines>;
[JSONName('lines')]
FLinesArray: TArray<TQuotationLines>;
function GetLines: TObjectList<TQuotationLines>;
published
property Cash_Van_Id: Integer read FCash_Van_Id write FCash_Van_Id;
property Data: TDate read FData write FData;
property Partner_Id: Integer read FPartner_Id write FPartner_Id;
property Partner_Invoice_Id:Integer read FPartner_Invoice_Id write FPartner_Invoice_Id;
property Partner_Shipping_Id:Integer read FPartner_Shipping_Id write FPartner_Shipping_Id;
property Pricelist_Id: Integer read FPricelist_Id write FPricelist_Id;
property Lines: TObjectList<TQuotationLines> read GetLines;
destructor Destroy; override;
end;
implementation
{ TQuotationInvoice }
destructor TQuotationInvoice.Destroy;
begin
GetLines.Free;
inherited;
end;
function TQuotationInvoice.GetLines: TObjectList<TQuotationLines>;
begin
if not Assigned(FLines) then
begin
FLines := TObjectList<TQuotationLines>.Create;
FLines.AddRange(FLinesArray);
end;
Result := FLines;
end;
end.
in my from i add in the uses the class name and "Q" is TQuotationInvoice created in Public session , I create this procedure (Below), if i give the (Q.Partner_Shipping_Id) const number like (Q.Partner_Shipping_Id:=1) it work fine but when i pass a variable like (Q.Partner_Shipping_Id:=AshippingID) show error "Invalid Class Typecast"
procedure AddQuotation(ApartnerID,AshippingID,APriceListID:Integer);
begin
Q.Cash_Van_Id:=POSID.ToInteger;
Q.Data:=Date;
Q.Partner_Id:=ApartnerID;
Q.Partner_Shipping_Id:=AshippingID; // <---------------------- Here the Error
Q.Pricelist_Id:=APriceListID;
end;
any Ideas ?