.Net Framework to .Net Core Migration Tools

Migrating from .NET Framework to .NET (often still informally called “.NET Core”) usually involves three areas:

• Project conversion (old .csproj → SDK-style)
• API compatibility analysis
• Code/package/runtime migration
• Testing and deployment modernization

A fully automatic migration is rare for large enterprise apps, but several tools can automate major portions of the work.

Understanding the migration process from .NET Framework to .NET Core will help you choose the right tools and avoid common compatibility issues.

Main Automatic & Semi-Automatic Migration Tools

1. .NET Upgrade Assistant

Official Microsoft migration tool and the most important one today.

What it does?

• Converts old project files to SDK-style projects
• Upgrades target frameworks
• Replaces unsupported APIs when possible
• Migrates package references
• Updates configuration files
• Helps move from:
  - .NET Framework → .NET 6/7/8+
  - ASP.NET MVC → ASP.NET Core
  - WPF / WinForms modernization
• Performs step-by-step guided upgrades

Supported app types

• Console apps
• Class libraries
• ASP.NET MVC
• Web API
• WinForms
• WPF

How it works

You install it as a .NET global tool:

dotnet tool install -g upgrade-assistant

Run:

upgrade-assistant upgrade MySolution.sln

The tool:

• analyzes dependencies
• upgrades projects one at a time
• generates reports
• applies automated fixes

Strengths

• Official Microsoft-supported
• Best ecosystem support
• Continuously updated
• Handles multi-project solutions

Limitations

• Cannot fully rewrite complex legacy architecture
• Web Forms support is limited
• Third-party dependencies may still require manual work

Best for: Most enterprise migrations.

2. try-convert

A Microsoft tool focused specifically on converting old project files.

What it does?

• Converts legacy .csproj to SDK-style format
• Simplifies project structure
• Updates package references

Example

try-convert -w MyProject.csproj

Strengths

• Fast and lightweight
• Good first step before larger migration

Limitations

• Does NOT fully migrate application code
• No API modernization
• No ASP.NET Core conversion

Best for: Library and backend projects where you mainly need SDK-style conversion.

3. Portability Analyzer (.NET Portability Analyzer)

Compatibility assessment tool from Microsoft.

What it does?

• Scans assemblies/projects
• Detects APIs unsupported in .NET Core/.NET
• Generates compatibility reports

Reports show:

• unsupported APIs
• estimated portability percentage
• replacement recommendations

Strengths

• Excellent for planning
• Helps estimate migration effort

Limitations

• Analysis only
• Does not rewrite code

Best for: Large legacy systems before migration begins.

4. API Port

Older Microsoft API compatibility analyzer.

What it does?

• Analyzes assemblies
• Checks .NET compatibility
• Suggests supported target frameworks

Largely superseded by:

• Upgrade Assistant
• built-in analyzers

But still useful for older enterprise systems.

Best for: Preliminary assessment of old libraries.

5. Windows Compatibility Pack

Not a migration tool itself, but extremely important.

What it does?

Provides missing APIs from:

• registry
• event log
• configuration
• directory services
• Windows-specific features

Why it matters?

Allows many legacy applications to compile on modern .NET with minimal changes.

Best for: Enterprise Windows applications.

6. .NET Analyzers

Roslyn-based analyzers integrated into modern .NET SDKs.

What they do?

• Detect obsolete APIs
• Suggest replacements
• Flag platform-specific code
• Recommend performance improvements

Strengths

• Continuous automated guidance
• Works inside Visual Studio

Best for: Incremental modernization after migration.

7. ReSharper .NET Upgrade Assistance

From JetBrains.

What it does?

• Detects deprecated APIs
• Offers automated refactoring
• Suggests modern syntax/features
• Helps migrate async patterns, LINQ usage, nullable references, etc.

Strengths

• Powerful code refactoring
• Excellent developer productivity

Limitations

• Commercial tool
• Not a complete migration framework

Best for: Large codebases with heavy refactoring needs.

8. Telerik Project Converter

Specialized migration utility for Telerik-based apps.

What it does?

• Updates Telerik references
• Migrates project configurations

Best for: Legacy apps using Telerik UI components.

Cloud & Enterprise Migration Platforms

9. AWS Porting Assistant for .NET

From Amazon Web Services.

What it does?

• Scans .NET Framework apps
• Identifies incompatible APIs/packages
• Suggests replacements
• Estimates migration effort
• Integrates with Upgrade Assistant

Strong feature: Dependency/package analysis is excellent.

Best for: Enterprise systems moving to AWS/cloud-native environments.

10. Azure Migrate

From Microsoft.

What it does?

Infrastructure + application assessment
Cloud readiness analysis
Dependency mapping
App modernization planning

Best for: Large enterprise migration programs.

Web Forms Migration Tools

11. System.Web Adapters

Important bridge technology from Microsoft.

What it does?

Helps migrate:

• ASP.NET Web Forms
• old System.Web dependencies

toward:

• ASP.NET Core

Strengths: Allows incremental migration instead of full rewrite.

Best for: Massive legacy ASP.NET applications.

12. YARP (Yet Another Reverse Proxy)

From Microsoft.

What it does?

Supports incremental migration:

• old .NET Framework app runs beside new ASP.NET Core app
• routes requests gradually

Best for: Strangler-pattern migrations.

Recommended Migration Strategy

Small Applications

Use:

• Upgrade Assistant
• SDK-style conversion
• Manual fixes

Medium Enterprise Apps

Use:

• Portability Analyzer
• AWS Porting Assistant or Upgrade Assistant
• ReSharper
• Incremental testing

Large Legacy ASP.NET/Web Forms Systems

Use:

• System.Web Adapters
• YARP
• Incremental strangler migration
• Upgrade Assistant where possible

Which Tools Are Most Important Today?

If you only choose a few:

What Cannot Be Fully Automated?

Automatic tools usually cannot fully migrate:

• ASP.NET Web Forms UI
• WCF server implementations
• COM interop-heavy systems
• Reflection-heavy frameworks
• Old authentication systems
• IIS-specific behaviors
• Complex desktop installers

These typically require architectural redesign.