What’s New in .NET 9: A Comprehensive Guide

In our previous blog, we talked about all the exciting updates that came with .NET 8 and hinted at something even bigger on the horizon. Well, the wait is over! .NET 9 is finally here, and it’s bringing some fantastic improvements that are sure to grab the attention of developers and businesses alike. The .net 9 release date was on November 12, 2024.

The DotNet latest version has been released creating a sense of excitement among developers and businesses equally. The latest release comes with optimizations, new features and enhancements that has been aimed at boosting performance and productivity in general, affecting .NET development services positively.

Here in this blog, we will be taking a peek into the new features and enhancements that has been released with .NET 9 version.

Without much ado, let’s begin.

What’s New With .NET 9?

.NET 9 brings to the table a number of notable improvements. It is the latest version of Microsoft dotnet core. Now this includes default support for DATAS, feature switches with attribute model, experimental SVE support and much more. Together, these feature enhancements are focused on helping developers build robust and dynamic applications by boosting their development experience to the next level.

So, let’s see these improvements.

Feature switches get a new attribute model

The latest .NET 9 upgrades have improved coding profusely. A new attribute model has been introduced in here for feature switches which also supports the built-in trimming of runtime. Feature switches is a functionality that lets developers enable or disable certain features within the .NET application by following the ‘if’ conditions.

The latest release comes with two new attributes for feature switches, namely FeatureSwitchDefinitionAttribute and FeatureGuardAttribute. It helps in the experimentation and testing of different application versions by turning off the respective code. As the extra codes can be easily removed, it helps developers build lightweight applications.

Garbage collection with default DATA

.NET team has enabled DATAS (Dynamic Adaptation to Application Sizes) as default Garbage collection to enhance the performance, stability and scalability of applications. This was earlier introduced as an opt-in feature in the .NET 8 version.

DATAS GC can adjust with the memory needs of an application. This way the heap size for the application also gets adjusted based on the workload. This was not possible earlier as the default Server GC was not flexible in adjusting the heap size with the application.

ARM SVE Support (experimental)

Integration of ARM Scalable Vector Extension support is another key upgrade in the dotnet latest version which is .Net 9. It helps with vectorisation that lets a .NET development company to work on high-performance computing applications. Developers can use the SVE .NET API to write efficient codes by using the latest hardware architectures.

Common parameters for UnsafeAccessorAttribute

It was in .NET 8 that UnsafeAccessorAttribute was introduced to let the caller have unsafe access to type members. With .NET 9, now this feature gets support for generic parameters for CoreCLR and AOT scenarios which was not provided earlier.

Default CET Enabled

.NET 9 enables CET (Control-flow Enforcement Technology) by default. It has been introduced to protect applications against the exploits of return-oriented programming. It protects against ROP by implementing stack protection that is based on hardware. Developers have the option to whether opt in or opt out of this feature.

Improvements in terms of performance

In this latest release, the .NET team has put in some effort to make improvements in terms of performance, which will improve the overall performance of the application apart from boosting developer experience.

Some of the key performance enhancements that have been made with this latest release are as follows:

• Loop Optimizations: Several loop optimization improvements have been made in here like post-indexed addressing and induction-variable widening to optimize the access of memory with loop-index variables. Loop counter variable direction and strength reduction are some of the compiler optimizations that has been included in there.
• New Constant Folding: New constant-folding features like floating-point numbers and SMID gets support with this latest .NET 9 version release.
• Better Exception Handling: To improve the performance of exception handling, CoreCRL gets a new approach.
• AVX10v1: Intel provides an SMID instruction set called Advanced Vector Extensions, and for the same, support has been provided by .NET 9.
• Improved PGO implementation: .NET 9 also helps with better PGO implementation by profiling code patterns to larger numbers.
• Reduced Address Exposure: .NET 9 tracks the usage of local variables by removing all kinds of unnecessary address exposure, and it does this with the help of the JIT compiler.

Enhancements in .NET libraries

To aggregate state by key two new methods called ‘CountBy’ and ‘AggregateBy’ has been added to LINQ. These methods save the developers from the task of allocating intermediate groupings which are generally carried out by the method called ‘GroupBy’.

There is also the inclusion of one-shot hash method along with the improvements in cryptography. Moreover, for encryption, KMAC algorithm will be leveraged by the new classes added in .NET 9.

With this latest .NET version, you can remove all the errors that are caused by floating-point calculation imprecisions. This has been made possible by the new From* methods that come with the TimeSpan class. It helps you build a TimeSpan object by using an int.

You can update the priority of the item in the queue by leveraging the Remove(TElement, TElement, TPriority, IEqualityComparer<TELement>) method that comes with the PriorityQueue<TElement, TPriority>

There has been updates in terms of collection types too. You can now make use of System.Collections.Generic for the same.

Just like many additions, there has been some removals too. This includes the removal of BinaryFormatter from .NET 9. Developers who used to depend on this feature will now be moving to alternatives like XmlSerializer, System.Text.Json and others to address the security concerns. Developers will be required to safeguard certificates and API keys securely and this will be made possible by using ByteHide Secrets. It will ensure they are stored and managed securely, even if changes are made to the application.

Enhancements in terms of .NET SDK

The latest .NET feature indicates a group of workloads in the SDK by using a specific version number and this has been made possible by the new feature called as workload sets. The workload-set update mode can have the version number included along with commands like install, update or restore.

Unit testing improved with the integration of MSBuild. Apart from that, NuGet security audit has also got improved and now by default it has direct and transitive package references. There has also been update in terms of MSBuild Script Analyzers.

The usability of the terminal logger has been improved, and it has been set to default.

.NET Aspire

With Microsoft .NET Core and .NET Aspire 9, some key updates are introduced to optimize and manage distributed applications with ease. These updates focus on improving the developer experience and interactivity.

.NET Aspire 9 comes with a mobile compatible dashboard which lets you manage the application from mobile devices. The resource lifecycle management with this update has made it easier to make quick changes to containers, projects or executables.

This .net latest version comes with powerful and advanced Telemetry with advanced filters to filter traces and browser integration with OpenTelemetry to send metrics, traces and structured logs to dashboard.

.Net 8 vs .Net 9: Which is Better?

Selecting between .NET 8 and .NET 9 is not about selecting which one is better—it is about understanding how new features integrated into .NET 9 improve what was given in .NET 8. Each has its advantages, however .NET 9 is the new version of .NET 8 that provides developers and companies even more benefits.

Here’s a closer look at how they compare:

Performance Enhancements

In NET 8, many improvements were made concerning the execution speed and fluency of applications.NET 9 extends this yet further, providing, better runtime performance and consumption of memory. This is a clear implication of improved performance of application software even under conditions of massive workload.

New Features and Tools

While .NET 8 marked a highly major update with some completely revolutionizing features, .NET 9 is bringing even more new features in areas like debugging, APIs, and integration with many new technologies. All these additions make some highly complex development tasks much easier and assist developers in coding.

Backward Compatibility

Another of .NET’s assets is that it has been created with design for backward compatibility in mind.NET 9 also guarantees usability for existing .NET 8 applications hence creating a platform that does not require massive overhauls. It is aimed at .NET 8 but is compatible with the existing solutions which had been developed using the 8 version.

Productivity Improvements

Both versions focus on empowering developers, but .NET 9 introduces smarter workflows, enhanced libraries, and refined tooling. These updates make coding faster, reduce errors, and improve collaboration across teams.

Security Updates

Each later edition of .NET framework has strong security improvements, it means that .NET 9 had also strong improvements in it. It stands on the security profile of .NET 8 and gives additional layers of security to maintain the application safe and secure.

Which Should You Choose?

For those still using .NET 8, they are encouraged to upgrade to .NET 9. Here we are not discussing an evolution but revolution in tools and features that augment efficiency, safety, and fun within a development cycle. When beginning a new project, it is better to start a project with .NET 9 as this presents you with all the new developments in this area.

Final Thought

Here is the update from the .NET team again.

.NET introduces a number of tools and components that are aimed at satisfying the requirements of modern applications by easing the entire development cycle and enhancing efficiency. Therefore, it can be argued that the task and purpose of .NET 9 will be massive in the development of optimized, secure and innovative applications by giving developers the required boosting through .NET 9 support.