Good Day Satyadnet
In Companies sometimes you will find people who think they know while they don't. Who can argue that the BLL is the middle man between the UI and the DAL. if you find an interviewer that does not know the meaning of DAL or BLL it will be useless to tell him about the communication that it does, i think the best approach is to tell him the advantages of building applications in N-Tier Application. let me give some good Advantages
1) BLL makes sure that the Business Rules are not Broken. There are some other validations that cannot be done on the Client side because they require complex calculation and the data can only be available in the Middle layer, in that case the BLL is the best place to Validate those Business Rules.
2) N-Tier Applications are simple to maintain, Because if you want to add one Functionality , you know that you will change your code in 3 places
3) Let us say you have an windows Application and your client say we need to expand our business and take it to the web. This will be costly because the Application needs to be written for web and that means what works in your windows application will not work for your web application. But if you have build your application as an N-Tier Application, you can take those BLL and DAL DLL's(Layers) and port them to any UI(Presentation Layer) they dont need to change, a Developer will only create an UI(ASP.NET) pages and call the function than redevelop the application from scratch.
Building Applications in Tiers is the Best thing to do and almost every company that understand what they do , they are doing this. Look at the architecture of MVC , its pretty much the same.
I have written some few articles on N-Tier Development, you can find them here.
Thank you for posting at Dotnetfunda
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