.NET Core Migration Strategy Guide

Oct 31, 2025 |

9 minutes read

Introduction to .NET Core Migration Strategy

Migrating from the legacy .NET Framework to .NET Core or .NET 6+ is no longer just a modernization option—it’s a strategic necessity. As Microsoft phases out support for the .NET Framework, organizations are transitioning to the new, unified .NET platform for better performance, cross-platform compatibility, and long-term stability.

Why Migrate to .NET Core?

The benefits of migration go far beyond version upgrades. The new .NET ecosystem delivers measurable improvements across performance, scalability, and maintainability.

Key Benefits

- Up to 50% better performance and faster response times
- Cross-platform deployment across Windows, Linux, and macOS
- Reduced memory footprint and improved resource utilization
- Long-term Microsoft support with continuous updates
- Access to modern development features like minimal APIs and gRPC

Migration Challenges

Migrating a production-grade application comes with its share of hurdles. Awareness of these challenges upfront helps you design a smoother migration path.

Common Challenges:

Breaking API or namespace changes
Outdated third-party dependencies
Configuration model differences (web.config → appsettings.json)
Testing and validation overhead
New deployment pipelines and tooling

Migration Assessment Strategy

Before diving into migration, conduct a detailed assessment of your existing application. This helps you identify which components can be migrated directly and which need to be re-engineered.

1. Application Analysis

Use the .NET Portability Analyzer to evaluate how compatible your current assemblies are with .NET Core.


dotnet tool install -g Microsoft.DotNet.ApiPortability.GlobalTool
ApiPort analyze -f "C:\YourApp\bin" -r Excel

2. Dependency Assessment

Component	Framework Support	Migration Path	Effort
ASP.NET MVC	Full Support	Direct migration	Low
Web Forms	No Support	Rewrite to MVC/Razor Pages	High
Entity Framework	Partial Support	Upgrade to EF Core	Medium
WCF Services	Limited Support	Move to gRPC / Web API	High

Step-by-Step Migration Process

Follow these steps to ensure a clean, risk-free migration from .NET Framework to .NET 6+.

Step 1: Create a New .NET Core Project

Start fresh with a new project structure to leverage modern patterns.


dotnet new web -n YourApp.Corecd YourApp.Core
# Add essential packagesdotnet add package Microsoft.EntityFrameworkCore.SqlServer
dotnet add package Microsoft.AspNetCore.Authentication.JwtBearer

Step 2: Update Configuration

Replace web.config with appsettings.json for a flexible, environment-based configuration system.


{"ConnectionStrings": {"DefaultConnection": "Server=.;Database=YourApp;Trusted_Connection=true"},"Jwt": {"Key": "YourSecretKey","Issuer": "YourApp","Audience": "YourApp"},"Logging": {"LogLevel": {"Default": "Information","Microsoft.AspNetCore": "Warning"}} }

Step 3: Migrate Controllers and Services

Migrate controllers to use dependency injection and API attributes.

Old .NET Framework Controller:


public class ProductController : Controller{
    private readonly IProductService _productService;

    public ProductController()
    {
        _productService = new ProductService();
    }
}

New .NET Core Controller:


[ApiController]
[Route("api/[controller]")]public class ProductController : ControllerBase{
    private readonly IProductService _productService;

    public ProductController(IProductService productService)
    {
        _productService = productService;
    }
}

Common Migration Patterns

Below are some of the most common migration practices used in real-world .NET modernization projects.

Entity Framework Core Setup


var builder = WebApplication.CreateBuilder(args);
// Register EF Corebuilder.Services.AddDbContext(options =>
    options.UseSqlServer(builder.Configuration.GetConnectionString("DefaultConnection")));

builder.Services.AddScoped();
var app = builder.Build();
// Configure middleware if (app.Environment.IsDevelopment())
{
    app.UseDeveloperExceptionPage();
}

app.UseHttpsRedirection();
app.UseAuthentication();
app.UseAuthorization();

app.MapControllers();
app.Run();

Authentication Migration

Implement modern JWT-based authentication in .NET Core:


builder.Services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
    .AddJwtBearer(options =>
    {
        options.TokenValidationParameters = new TokenValidationParameters
        {
            ValidateIssuer = true,
            ValidateAudience = true,
            ValidateLifetime = true,
            ValidateIssuerSigningKey = true,
            ValidIssuer = builder.Configuration["Jwt:Issuer"],
            ValidAudience = builder.Configuration["Jwt:Audience"],
            IssuerSigningKey = new SymmetricSecurityKey(
                Encoding.UTF8.GetBytes(builder.Configuration["Jwt:Key"]))
        };
    });

Testing and Validation

Testing is a non-negotiable part of migration. Before deployment, ensure your migrated application passes rigorous functional and performance checks.

Boost .NET Testing Today!

The Way Forward

Migrating to .NET Core is more than just modernizing your tech stack — it’s about future-proofing applications for performance, security, and scalability. A phased, well-documented approach minimizes disruption and ensures long-term ROI.

Continue enhancing your applications by leveraging containerization, cloud services, and CI/CD pipelines — enabling faster delivery and smoother evolution with every release.

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Gaurang Jadav

Oct 31 2025

Dynamic and results-driven eCommerce leader with 17 years of experience in developing, managing, and scaling successful online businesses. Proven expertise in driving digital transformation, optimizing operations, and delivering exceptional customer experiences to enhance revenue growth and brand presence. A visionary strategist with a strong track record in leveraging cutting-edge technologies and omnichannel solutions to achieve competitive advantage in global markets.