There are a lot of companies that I've come across since I started freelancing who have a .Net application built by another agency or freelance developer only to have those developers leave and now the company is stuck trying to maintain the app on their own. That's a problem because these companies don't have the staff or knowledge to maintain the applications after the original creators are gone. You can make this argument for any software development project, but I'm stalking specifically about .Net projects. The companies hire me to come in and save their project. A situation my friend Matt has coined as a .Net Rescue Project - a term I'm a huge fan of.
These projects fall apart for a variety of reasons—contract developers lose interest and move on to greener pastures, agencies burn through their contract dollars until the owner decides to cut bait and end the relationship. I have a lot of theories about why this happens.
Many companies that come to me have outdated .NET frameworks. Sometimes, the original creator didn’t bail on them—the project was simply completed. But now, six or seven years later, things are breaking. .NET has moved on. Dependencies that were fine then are now unsupported, vulnerable, or outright failing. At the time, no one thought about long-term maintenance or upgrades.
The Real Problems with Legacy .NET Projects
LIke I said, legacy projects fail for a variety of reasons. The code has often been abandoned for so long that it’s barely usable. Frameworks become outdated, dependencies are unsupported, and no one with the right skills is available to fix these issues. Over time, security risks creep in—especially if the framework is no longer supported. Moving from .NET Framework to .NET Core is a major leap, but even smaller upgrades (like .NET Core 2.1 to 3.0 and beyond) can introduce unexpected challenges.
Each upgrade comes with critical security fixes, but if a company doesn’t have staff or an agency contract to handle the migration, the project just sits idle. Every day that passes increases the risk of a compromised system.
Another reason these projects fail is that companies ignore the problem until it’s too late. Eventually, an external API will stop supporting the version your legacy app is using. When that happens, the company risks losing money, especially if the API is tied to something like a payment processor or an invoice system.
A good example is the QuickBooks API. Recently the company announced they were discontinuing support for an older API version. One of my clients depended on that version for their .NET Core 2.1 app. We had to update their code to work with the new version before it was too late, or they would have lost the ability to process payments.
The Wrong Way to Fix Legacy Projects
The biggest mistake companies make when trying to fix a failing .NET project is hiring a junior developer or someone without deep .NET experience. They either patch issues with quick fixes instead of addressing the root problem or hack in new features on top of an unstable foundation. This approach makes things worse. But I don’t blame businesses for it—their job is the business, not the tech. When things break, they get into the mindset of "just fix the thing". But this thinking is not a good long term solution to the problem.
The Right Approach to Fixing Legacy .NET Applications
To keep legacy .NET applications running long-term, companies need to take a structured approach. The first step is consistently monitoring the framework in use. Is it approaching end-of-life? How soon? Can you get away with running the current version for a little longer? What upgrade paths do we have?
Having a long-term plan in place is critical. At the time of development, businesses should think about maintenance—what will it take to keep this system running in five or ten years? Too often, maintenance is treated as an afterthought. With all my clients, after the initial project is completed I will present a maintenance contract that covers updates and ongoing maintenance. This way there is never a gap in coverage and the business can worry about it's business and I'll worry about the tech stack.
Good documentation matters. A new developer should be able to step in and understand how the application works. Businesses should make documentation a required part of any development contract, not an optional deliverable. I can't tell you how many times I've had to ask a business why some techical architecture decision was made. More times than not, the business has no idea why something was done the way it was.
Automated testing is another key factor. When updating a legacy codebase, regression errors are a major risk, especially when the person doing the update didn’t write the original code. Without a solid test suite, even a minor change can break something critical.
Key Takeaways
Legacy .NET projects don’t fail because the tech is bad—they fail because they are left behind. Sometimes initial objectives were never fully met before the original development company moved on. Other times, businesses treated the project as a one-and-done investment without considering long-term maintenance.
With the right strategy and approach, these systems can be rescued and maintained. But ignoring technical debt isn’t an option. Just like operating systems need updates to stay secure, applications need regular checkups. If a company wants to avoid ending up in the same situation again in a few years, they need to have a plan.
Work with an experienced .NET consultant who knows how to keep legacy applications alive and running smoothly. A structured, stable approach can save your business from expensive, last-minute emergencies.
If your company is struggling with an outdated .NET project and needs an expert to get things back on track, contact me here to start a conversation.