Migrating from .NET 8 to .NET 9 Print

Overview

.NET 9 is a Standard Term Support (STS) release with enhanced performance and new features. If you need long-term stability, consider staying on .NET 8 LTS or waiting for .NET 10 LTS.

What is New in .NET 9?

• Performance: Further optimizations in JIT and GC
• Blazor: Improved static rendering and hydration
• Minimal APIs: Enhanced OpenAPI support
• LINQ: New methods like CountBy, Index

Step 1: Update Target Framework

Edit your .csproj file:

<!-- Before -->
<TargetFramework>net8.0</TargetFramework>

<!-- After -->
<TargetFramework>net9.0</TargetFramework>

Step 2: Update NuGet Packages

Update all Microsoft.* packages to 9.x:

dotnet outdated --upgrade

Step 3: Key Breaking Changes

• Obsolete APIs: Some APIs marked obsolete in .NET 8 may be removed
• Behavioral Changes: Review Microsoft's breaking changes documentation
• Package Updates: Third-party packages may need updates

Step 4: Blazor Updates

If using Blazor, review new features:

• Improved static SSR (Server-Side Rendering)
• Enhanced form handling
• Better hydration performance

Step 5: Test and Build

dotnet clean
dotnet build
dotnet test
dotnet run

Step 6: Update Plesk Configuration

1. Log in to Plesk control panel
2. Navigate to Websites & Domains → your domain
3. Click Hosting Settings
4. Set .NET Core Version to 9.0.x
5. Save changes

Step 7: Publish and Deploy

dotnet publish -c Release -o ./publish

Deploy via Web Deploy or FTP to your Plesk hosting.

Considerations

• .NET 9 is STS - supported for 18 months
• For production apps, .NET 8 LTS may be more appropriate
• Plan migration to .NET 10 LTS when available