[Solved] Subtract values of two columns using SQL Server and display in ASP.Net GridView

and my query

SELECT dis.AdmissionNo,ReferenceNo,SName,FName,ParentID,Amount,Discount,Total 
FROM tblDiscount as dis 
inner join tblStdReg as sr on sr.AdmissionNo=dis.AdmissionNo

and tblDiscount:

ClassID,SectionID,AdmissionNo,Amount,Discount

how to show total after deducted such as

Amount-Discount = Total