Is MVC Replacing ASP.NET Web Forms?

Architectural Thinking: Brownfield Vs Greenfield Applications

All software applications you have worked or will work in future are either Brownfield or Greenfield.

• Brownfield Development: When any existing or legacy applications need to have new features or changes to address business needs, it is known as brownfield. In such situations, unless you are building a new module or component, you have less, limited or no scope to use new architectural styles, patterns and so on. The very reason of such limitations is because those old applications are built using an old version of technologies and the latest versions of one technology/framework and many are not be compatible with old versions.
  
• Greenfield Development: When a brand-new project is being envisioned and no previous work is done in that or a related area then it's called Greenfield. In the software industry it doesn't happen very often. But whenever it happens its the architect's responsibility to determine what the best technology is to address business needs.

Hence, it's not appropriate to say that because MVC is so new hence every new web application must be made using MVC or if WPF is available in addition to Windows Forms so every desktop application must be made using WPF. Whatever is the case neither ASP.NET Web Forms nor Windows Forms can be totally ignored.

Why and Why not the Latest Technologies should be chosen

First the reasons why not.

1. It's Brownfield and new technology doesn't fit anywhere.
2. If new technology or versions are introduced then it will cause many build errors due to outdated references of non-supported library references.
3. Business goals and software quality are not compromised by continuing to use current and available technologies like ASP.NET Web Forms over MVC or Windows Forms over WPF.
4. You are not investing money in any extra off-the-shelf tools to handle issues that could have been handled by the latest versions of similar area of technologies, for example MVC instead of ASP.NET Web Forms, or WPF over Windows Forms.
5. Teams often might not have a certain skill set that allows them to proceed with development using new technology options
6. Budget allocation from a client often may impact your decision to use and develop using the latest technologies.
7. If the core/bestselling features of a new candidate technology (MVC or WPF) are not being used at least up to 50% then you have done nothing.
8. Considering how soon the client and business wants to have an application ready, it turns being a major factor to dictate the technology of choice.
9. The client and business doesn't care how you do it; what matters is the end-result and a workable / good-enough software.
10. No way to use old legacy downstream applications with the latest available technologies.

Why develop using Latest Technologies

1. Greenfield software solution and no legacy or old piece of code is being used.
2. Focus is more on Robustness, Testability, Object Oriented design and quality. (This doesn't mean previous technology can't accomplish these; it's about ease and in-built features and offerings).
3. Amazing team with great skills to learn new technologies and adapt the changes.
4. Company's vision is to showcase products build using latest technologies.
5. Client themselves want the solution to be developed using latest technologies and have budget to support that.

Why MVC over ASP.NET Web Forms then

Note: this section assumes that you are aware of MVC benefits and the general technical terms used below.

1. Separation of Concerns is the core of MVC.
2. Single Responsibility Principle is done by default.
3. Unified and even better framework to work on WebAPI, Mobile, HTML 5, CSS3, Security and Deployment (including Azure).
4. Unit testing is easily done to have stable, robust and quality software solutions delivered continuously.
5. Fast screen generation for CRUD operations via Scaffolding.
6. Convention over configuration.

Summary

Based on my experience as an architect in the industry I would like to summarize that it's very hard for any organization to keep up with the latest version and technologies all the time because by the time you become comfortable with one version the newer is around the corner. So if you are working on MVC 4, then see if you can learn and try some application being developed on your own. Or if you just happen to be in the ASP.NET Web Forms world until now then I would encourage you to try converting that application to MVC for your personal benefit.

This will force you to learn new technology and apply that learning. If you have made some progress in that then in the next interview you can proudly showcase your MVC knowledge and say that you have migrated ASP.NET Web Forms to MVC.

“Regardless of what you are using to make a living out of a job, you need to learn new ones to build a Career.”