.NET 7 Preview 1 is officially released

​Recently, the first preview version of .NET 7, .NET 7 Preview 1, was officially released.

.NET 7 builds on the foundation established by .NET 6 and includes a unified set of base libraries, runtimes, and SDKs that simplify the development experience and improve developer productivity. Key areas of focus for .NET 7 include improved support for cloud-native scenarios, tools to make it easier to upgrade legacy projects, and simplifying the developer experience by making it easier to use containers.

.NET 7 Preview1 includes nullable annotations for APIs, ongoing JIT compiler optimizations, new APIs, and support for more hot-reloading scenarios.

.NET 7 Preview 1 Major Updates

Nullable annotations for Microsoft.Extensions

.NET has made progress in annotating the Microsoft.Extensions.* libraries for nullability. In .NET 7 Preview 1, the following libraries have been annotated for nullability:

• Microsoft.Extensions.DependencyInjection.Abstractions
• Microsoft.Extensions.Logging.Abstractions
• Microsoft.Extensions.Primitives
• Microsoft.Extensions.FileSystemGlobbing
• Microsoft.Extensions.DependencyModel
• Microsoft.Extensions.Configuration.Abstractions
• Microsoft.Extensions.FileProviders.Abstractions
• Microsoft.Extensions.FileProviders.Physical
• Microsoft.Extensions.Configuration
• Microsoft.Extensions.Configuration.Binder
• Microsoft.Extensions.Configuration.CommandLine
• Microsoft.Extensions.Configuration.EnvironmentVariables
• Microsoft.Extensions.Configuration.FileExtensions
• Microsoft.Extensions.Configuration.Ini
• Microsoft.Extensions.Configuration.Json

We plan to add nullability annotations to all Microsoft.Extensions.* libraries when .NET 7 is officially released.

observability

Continue to improve the tracking API:

• Added ActivityContext.TryParse overload to allow parsing and creation of ActivityContext objects, including whether to propagate the activity context from the remote parent (related issue).
• Add Activity.IsStopped method to indicate whether the Activity object is stopped (related question).

code generation

Code generation improvements based on community input

• Convert some legacy intrinsics to NamedIntrinsic. #62271
• Add additional binary operations to RangeCheck analysis. #61662
• [JIT] [61620] Optimize ARM64 for *x = dblCns; #61847
• CoreRT supports ARM64&Unix. #41023
• Override based FMA codegen optimization #58196

Dynamic PGO

• OSR support for Arm64
• JIT: OSR with support for synchronous methods
• JIT: Handling the interaction of OSR, PGO and tail calls
• Added 2009 Jit Architecture Plan (excerpt)
• JIT: forward replacement for limited versions of some relops
• JIT: save generic context for post devirtualization

Arm64

Arm64: Memory Barrier Improvements

Loop optimization

• Generalized pre-loop header creation and loop promotion
• Loop refactoring and annotation improvements

Interop: p/Invoke code generation

We integrated the p/invoke Source Generator prototyped in .NET 6 into dotnet/runtime and have been converting the runtime library to use it. This means that the converted p/invokes are AOT compatible and no longer need to generate IL Stubs at runtime.

New API in System.Text.Json

System.Text.Json comes with some small lifecycle enhancements:

• Developers now have access to the default singleton JsonSerializerOptions used internally by System.Text.Json (related issue).
• Add a JsonWriterOptions.MaxDepth property and make sure this value comes from the serialized JsonSerializerOptions.MaxDepth equivalent property (related question).
• Add Patch method to System.Net.Http.Json

Hot reload improvements

The following changes apply to Blazor WebAssembly and C# Hot Reload for .NET

• Add static lambda to existing method
• Add a lambda that captures this to an existing method that already has at least one lambda that captures this
• Add a new static or non-virtual instance method to an existing class
• Add a new static field to an existing class
• add new class