Thank you so much your valuable feedback. I will keep in mind and train myself.
As a developer , currently I am learning and come into this scenario to add some fields in SalesInvoice Report. I know it's a very complex report.
I have analyzed that there is one class named "SalesInvoiceDP"
This class have three Temp Tables named
1. SalesInvoiceTemp
2. SalesInvoiceHeader
3. SalesInvoiceFooter
If I want to add some more fields in these Temp tables , how can I customize SalesInvoiceDP class?