I am new in D365 development..
i am learning from book named (cookbook) , there is topic about creating dialog using RunBase Class .
when applying this topic gave me an error

I copied the class to another class but same error
Here my code
class MyDialog extends RunBase
{
///
/// Runs the class with the specified arguments.
///
/// The specified arguments.
public static void main(Args _args)
{
DialogField fieldAccount,fieldName,fieldGroup,fieldCurrency,fieldPaymTermId,fieldPaymMode;
CustName CustName;
CustGroupId custGroupId;
CurrencyCode currencyCode;
CustPaymTermId PaymTermId;
CustPaymMode PaymMode;
}
public container pack()
{
return conNull();
}
public boolean unpack(container _packedClass)
{
return true;
}
Object dialog()
{
Dialog dialog;
DialogGroup groupCustomer,groupPayment;
DialogField fieldAccount,fieldName,fieldGroup,fieldCurrency,fieldPaymTermId,fieldPaymMode;
dialog = super();
dialog.caption("Customer information");
fieldAccount = dialog.addField(extendedTypeStr(CustVendAC),"Customer informations");
fieldName = dialog.addField(extendedTypeStr(CustName),"Customer name");
dialog.addTabPage("Details");
groupCustomer = dialog.addGroup("Setup");
fieldGroup = dialog.addField(extendedTypeStr(CustGroupId),"Customer group Id");
fieldCurrency = dialog.addField(extendedTypeStr(CurrencyCode),"Customer group Id");
groupPayment = dialog.addGroup("Payment");
fieldPaymTermId = dialog.addField(extendedTypeStr(CustPaymTermId));
fieldPaymMode = dialog.addField(extendedTypeStr(CustPaymMode));
return dialog;
}
public static void main(Args _arge)
{
MyDialog myDialog = new MyDialog();
if(mydialog.prompt())
{
myDialog.run();
}
}
}
My reference packages are : Application common - Application Foundation - Application Platform - Application Suite - Calendar - Contact Person - Currency - Dimension - Directory - and Ledger .
Thank you in advance .