Modernizing legacy .NET applications: Key concepts

If you update your .NET applications to the latest version, you will have many good things such as an improved quality of performance, access to new features, and increased protection. But the upgrading process might prove difficult. So where can we actually begin from? What particular conditions can make you think of updating your apps? What can help you choose the most appropriate .NET version? And what obstacles should you anticipate?

This article will aim to answer the questions above by looking into what goes into updating .NET applications nowadays. We’ll delve into the themes related to app modernization, key choices to consider, as well as possible obstacles that may arise. Whether you are dealing with legacy code or moving to another environment, we want to provide useful information that can aid in comprehending the path forward.

Legacy vs. modern .NET applications: The case for modernization

Migrating legacy applications, especially those developed based upon earlier versions of the .NET framework (ranging between 1. through 4.8) comprises moving from obsolete monolithic systems existing within on-premises servers towards increasingly adaptable cloud-native architectures (from.NET 5 onwards).

There are numerous typical hurdles confronting numerous old systems, though every outdated software represents particular obstacles in the modernization process.

The following diagram demonstrates the essential differences between traditional out-of-date software and modern cloud-based solutions.

Usually, a legacy .NET application is a monolith, based on the .NET Framework, running on a local Microsoft Windows server, and connected to the Microsoft SQL Server database. This may change according to your architecture; however, these .NET applications generally have such disadvantages as:

• On-premises server management: In order to manage an on-premises server system such as Windows and SQL Server, you have to expend a lot of administrative effort due to the high need for hardware maintenance along with updates and security patches.
• Dependency on Windows and licensing costs: Legacy systems rely on particular Windows-based environments, thus causing increased licensing costs and restricting flexibility in deployment.
• Upgradation and scaling problems: Implementing even minute changes can be quite a task with a monolithic architecture. Furthermore, scaling to meet increasing demand may be slower and resource-consuming.
• High maintenance and support costs: The complexity related to code of the aging platforms and the cost of hiring skilled personnel is increasing over time. The financial demands of maintaining outdated infrastructure often outweigh any benefits obtained from maintaining these systems in their current state.
• Data migration challenges: Migration and reorganization of old data takes a lot of time and can be complicated, especially when dealing with information stored in various systems. This makes it difficult to integrate it into newer platforms using modern tools and technologies.
• Security vulnerabilities: The older systems get, the higher the likelihood of security risks they have with the obsolete protocols coupled with unpatched vulnerabilities that may expose them to cyber-attacks and theft of data.
• Compliance and integration concerns: Many of those older applications find it hard to comply with current rules such as GDPR and CCPA. Moreover, integrating into modern tech solutions such as real-time data processing or AI-powered tools creates data silos and missed chances.

On the opposite, applications built for a cloud-based architecture offer several benefits:

• Minimal management overhead: With managed services of third-party providers, the integrated cloud solutions require less manual management of infrastructure. This way, they need few staff, and teams can concentrate on creating new products.
• No Windows dependency or licensing fee: Cloud applications get rid of their reliance on Windows using .NET Core and containers. Thereby, they cut down spending on licensing while ensuring their availability on different platforms.
• Agility with microservices and scalability:  Microservices mean you can release independently and frequently update, thereby enhancing agility, while elasticity in the cloud lets you assign resources dynamically based on usage.
• Cost-efficiency and flexibility: The cost-efficiency and flexibility enabled by serverless cloud architectures make it possible to plan better, optimizing resource usage within any budget while providing needed scalability precisely at the moment it is needed.

Running applications in a cloud environment is more efficient and financially viable compared to using a conventional on-premises approach. You have the freedom to choose where and when to deploy such applications when using a cloud-based model.

Selecting the right .NET version for your upgrade

Selecting an appropriate version of .NET mainly relies on the goals of your project. You have a choice between .NET Core, .NET 6, .NET 7 as well as .NET 8 which address diverse needs. Depending on whether you want continuity on an old platform, utilization of cloud-native capabilities, or getting your software ready for upcoming changes, there are distinctive benefits associated with every version.

Consider factors like your project’ timeline, long-term support requirements, and the new features that each release includes before you can make a well-grounded decision. Do you need to modernize with as little interference, or are you considering future-proofing your application? The following breakdown will help make sure the upgrade suits what you want specifically.

.NET Core – A flexible upgrade path

When select it?
Choose .NET Core if  you want to improve your old app with no major interference and guarantee an ability to be used on various platforms regardless of the highest updates.

Practical application:
.NET Core, being cross-platform and open-source, is a framework aimed to address various restrictions of the older .NET Framework. That is to say, it is the best choice if you want to upgrade an old application to a new and more efficient environment, and you have no need for new features that are only available in the newest .NET versions.

In legacy applications that require long-term stability, it is advantageous to utilize .NET Core 3.1 because it supports existing .NET framework code and various libraries.

.NET 6 – A solid, reliable foundation

When select it?
It would be perfect for legacy apps that work well but need some modifications to enhance stability and carry out cross-platform backing.

Practical application:
For businesses looking for fewer updates and stability, .NET 6 provides a solid and reliable platform. It is incredibly effective in cloud and mobile development because it has great runtime performance as well as cross-platform compatibility. The wide range of functionalities and ecosystem support indicates that despite the nearing of its official support window, it remains reliable for those looking to maintain their current applications without continually changing them.

.NET 7 – Optimized for high-performance and cloud integration

When select it?
Consider it for your projects where high performance and advanced cloud-native capabilities are essential. This version guarantees that you are in constant sync with technology if you don’t mind regular updates.

Practical application:
.NET 7 is tailored to suit the latest improvements that are intended to enable cloud environments and microservices. This makes it a good solution for teams that aim at using the most recent technologies due to its advanced capabilities such as improved memory performance, cloud native support, and better runtime performance. Despite being a short-term release that will be supported for only eighteen months, it is however suitable for high-performance applications that must always remain at the leading edge of technology.

.NET 8 – A future-ready platform for modern development

When select it? 

In case you are planning to either modernize or create new applications using recent tools, then .NET 8 is the best choice. If you are in need of a platform that will not be outdated shortly, then this is what you need.

Practical application:
Being launched in the last quarter of 2023, version eight of .NET is characterized by the most modern advancements in AI integration features and cloud-native building types. These include stuff like improved Native AOT backing as well as AI controlled libraries. .NET 8 is earmarked as an LTS (Long-Term Support) version providing stability into the future for entities that wish to remain ahead of the curve in terms of software development. The reason behind this is that it has been designed to focus on what will happen tomorrow rather than what has already transpired today, hence making it an excellent alternative for teams preparing themselves in terms of upgrading their software applications. 

Common strategies for migrating to the cloud

Given the fact that the latest .NET versions have been optimized for cloud-based apps, you would need to make a decision regarding migrating your already existing apps into this new environment. The following are some of the most popular migration strategies:

Rehosting (“Lift and Shift”): Cloud infrastructure-based applications

Rehosting is the process of moving an application from its current environment (usually on-premises) to a cloud environment with minimal or no changes.

• Key characteristic: Essentially, it’s a matter of “lifting” the app and “shifting” it to the cloud without altering its architecture or code.
• When to use: This path is commonly taken for a rapid transition with minimal disruption, in cases where organizations seek ways of cutting back on expenses by leveraging the scalability of cloud computing instead of writing new applications.
• Example: Migrating a virtual machine (VM) from an on-premises data center to a cloud VM.

Replatforming (“Lift, Tinker, and Shift”): Cloud-optimized applications

Replatforming involves making some changes to the application during the migration process to take better advantage of the cloud platform’s features (such as managed services or cloud-native infrastructure) but without a full redesign or re-architecture.

• Key characteristic: The application is "lifted" and "shifted," but certain components (like the database, operating system, or middleware) may be modified or replaced to better align with cloud services.
• When to use: This is appropriate when businesses want to optimize their application for the cloud without undertaking a full rewrite. It’s a middle-ground approach.
• Example: Moving an application to a cloud-based platform like AWS or Azure but changing the database engine (e.g., from Oracle to Amazon RDS).

Refactoring (Rewriting or Redesigning): Cloud-native application transformation

Refactoring involves making significant changes to the application’s code and architecture to optimize it for the cloud, often through re-architecting the application entirely to take full advantage of cloud-native services and modern development practices.

• Key characteristic: Refactoring typically requires a deep level of modification to the application’s source code, structure, and possibly its functionality. This is a more intensive process than re-platforming, involving redesigning parts of the application to make it scalable, resilient, and cloud-optimized.
• When to use: Consider refactoring if you want to take full advantage of advanced cloud-native capabilities (e.g., microservices, containers, serverless computing) or if your current application isn’t able to scale or work efficiently.
• Example: Breaking down a monolithic application into microservices or converting parts of the code to an orchestration platform such as Kubernetes.

Rebuilding: Cloud-native applications from scratch 

Rebuilding entails restructuring and rewriting an application from scratch, often by modern frameworks and cloud-native means to fully correlate with cloud capabilities.

• Key characteristic: Rebuilding is the most extensive migration plan that calls for a total overhaul of the application. It takes full advantage of modern cloud technologies, such as microservices, serverless computing, and containerization.
• When to use: Rebuilding makes sense when companies are all set to fully embrace the cloud and are looking for a new beginning to get rid of technical debt from the past. It’s the best choice when the application must be designed from scratch to scale effectively in the cloud and meet future demands.
• Example The entire application is rebuilt with cloud-native tools and architectures. 

Hybrid approach: Combining multiple strategies

The hybrid approach is a combination of rehosting, re-platforming, refactoring, and rebuilding processes that are put in place in order to realize an orderly strategy which is mutually beneficial, both in the short run and long run.

• Key characteristic:
  • Selective modernization: Certain sections of the application get rehosted fast for migration while others get refactored or rebuilt to take advantage of cloud-native capabilities over time.
  • Flexible timelines: Allows for step-by step migration, thereby diffusing the costs and risks that come along with modernization.
  • Tailor-made: It offers optimized specific parts of the application without changing every single part at the same time.
• When to use: Hybrid strategy is suitable for organizations that require a mix of rapid, low-risk wins as well as far-reaching renewal objectives. This strategy is ideal when some parts of the application need immediate cloud benefits, while others require more in-depth transformation.
• Example: A business might rehost its database but rebuild the core application logic to take advantage of microservices and serverless technologies. Here’s a table that summarizes the key differences between Rehosting, Replatforming, Refactoring, and Rebuilding:

How to choose the right modernization strategy

How can you decide which modernization plan is most appropriate for your case?  Start by analyzing your present situation and laying down concrete goals.  

1. Evaluate the state of your current application environment

Before you modernize your .NET applications, first look at how they are performing. Examine their architecture, pinpoint any cases of declining operation, and chart down your system’s dependencies. With this, you will be able to identify specific sections with problems like obsolete frameworks or security vulnerabilities, which might affect performance. The main aim is just to find out where these applications are lacking behind so to fix it during the modernizing process.

2. State clear business and technical objectives

After you’ve mapped out all your existing applications and processes, you should set your goals. Work with IT teams, business users and other stakeholders to come up with unambiguous objectives. What do you want to achieve through this change? Whether it’s improving application performance, supporting new business needs, or scaling for the future, having well-defined goals ensures everyone is aligned and provides a roadmap for your modernization efforts. It will also help guide your decisions when it comes to the technical aspects of the upgrade.

With a solid technical audit and clear business objectives, you’ll be in a much stronger position to decide on the right approach for your modernization. Your choice between rehosting, replatforming, refactoring, or rebuilding should be guided by what your application really requires, and what goals you hope to achieve using that application.  In each concrete case, this or that approach has its benefits only in relation to this exact situation. As such, while one app may require multiple improvements concurrently, the other may imply sufficient alterations using current resources only. 

Challenges of legacy .NET app modernization

Modernizing a .NET application legacy to run in cloud is an attractive choice because it is more flexible, can scale better and could potentially save money as opposed to supporting on-premises infrastructure. But these are some major stumbling blocks that await companies that would wish to migrate legacy applications into cloud, especially if they do not comprehend how complicated it can be. Below are the major hurdles which may accompany your shifting to cloud-based platforms and services:

1. Resource allocation for performance and security

Scaling to fit changing workloads in the cloud can be a challenge when porting a .NET application that was first run on your servers. Cloud platforms on the contrary, never stop requiring continuous allocation ensuring resources are available in the right portions. Over-provisioning will result in increased costs, under-provisioning leads to unsatisfactory running of the application by users.

Tip:
Use cloud cost management and monitoring tools to monitor usage, optimize resource allocation, and prevent over-provisioning or under-provisioning.

2. Bridging the skill gap

The transferring of your .NET applications to the cloud will often demand new tools usage and best practices adoption. If your developers and IT staff have been dealing with on premise environments only, then this change will necessitate improvement of your team’s competencies. Teams without any prior exposure to the cloud are overwhelmed by the myriad of services, including computing, storage, security, DevOps and automation.

Tip:
Invest in staff training and certifications to reduce any skills gap. Most cloud platforms provide assets, such as free courses, practical tasks as well as certification paths, that will allow your employees to enhance their expertise in clouding computing.

3. Legacy code and application compatibility

Cloud migration is one of the most challenging things since it involves ensuring that the old .NET applications run perfectly in such an environment. Over time, many companies do not realize how much technical debt has been accumulated, owing to continuous development over the years using outdated technology stacks. In order to maintain compatibility with cloud-native services, an old.NET application may still require significant rewrites or re-engineering in spite of the availability of cloud tools and services.

Tip:
Thoroughly inspect your current codebase before moving it. Look at places in which refactoring might be needed or improvement required, and use cloud development tools, gradually improving your app during migration.

4. Data migration and integration complexities

Migrating data securely from on-premises systems to the cloud presents yet another key hurdle. It is critical to transfer data without losing it or interrupting any important business activities. Such a step can be complicated by working on vast datasets or those considered important to the company.

Tip:
To ensure that the process of moving data is seamless, develop a complete strategy for moving data and make sure that there are plans for testing, validation, and rollback in place. Use data migration services and the cloud’s native tools to make the process simpler and ensure data integrity when data is being migrated.

Overview of a modern .NET tech stack

There are plenty of powerful tools and frameworks in the .NET environment that are built with the aim of enhancing development speed, optimizing performance, and guaranteeing scalability. To decide on which tools and frameworks will be most appropriate for your applications, you need to know the basic building blocks of current .NET technology stacks.

When considering cloud interfaces, effective data management, and expandable web solutions, you must only modernize your systems by choosing appropriate technologies that can keep up with these changes.

Conclusion

When it comes to migrating your legacy .NET applications to the cloud, there are clear benefits like reduced management overhead, better scalability, and potential cost savings. Nonetheless, the selection of an appropriate .NET version stands as a major guarantee for a smooth transition. When choosing from .NET Core, .NET 6, .NET 7б, and .NET 8 you always have to think whether this particular version is what your project requires.

If you accomplish a comprehensive technical audit and establish straightforward business objectives, you will manage to distinguish the best version along with the most efficient modernization strategy. Whether you choose rehosting, re-platforming, refactoring, or rebuilding, each approach offers distinct benefits depending on your goals.

Even if challenges like resource allocation, skill gaps, and data migration come into play, they can always be covered by strategic planning. Bringing your .NET applications up-to-date for cloud positioning allows you to a more flexible, scalable, and growing business.

FAQ

1. What version of .NET do I have?

To check your .NET version, use the ‘dotnet --version’ command in Command Prompt (Windows) or Terminal (macOS/Linux). This will return the version of the .NET SDK (including .NET Core) installed.

2. How to check .NET Framework version? 

There are several ways to check the .NET Framework version:

• Using Command Prompt

Run: reg query "HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full" /v Version

• Using PowerShell

Run: Get-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full" -Name Version

• Using Registry Editor

Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full

• Programs and features

Go to Control Panel > Programs > Programs and Features and look for installed .NET Framework versions.

3. How to migrate .NET application to Azure?

For a guide on the migration strategies, actionable insights, subsequent steps, and valued suggestions that you can implement on the go, view our blog post:  https://www.tymiq.com/post/your-complete-handbook-for-net-application-modernization-on-azure

4. How to improve performance of .NET application?

Improving the performance of a .NET application is a complex task that involves a number of components. The following are some suggestions you might find beneficial. In order to enhance the performance of your .NET application, you should try optimizing algorithms and minimizing memory allocations. Use caching (e.g., MemoryCache or Redis) to reduce database load and enhance speed. Improve database queries with proper indexing and use Dapper for lightweight access. Minimize garbage collection (GC) pressure with Span<T> and Memory<T>.

For faster startup, trim unused code with the Linker and apply lazy initialization. Use async/await for I/O-bound tasks and optimize concurrency for CPU-bound ones. Lastly, use tools such as dotTrace or Application Insights to follow up on the performance by your product, so as to benefit from the most recent .NET advancements.