Migration from ASP.NET Web Forms to ASP.NET Core involves several steps, as these frameworks have different architectures. This guide provides an overview of the migration process, focusing on key areas such as project structure, configuration, and code adjustments.

1. Understanding the Differences

ASP.NET Core is a complete rewrite of the ASP.NET framework, which means that many concepts and components have changed. Key differences include:

• ASP.NET Core uses a modular architecture, allowing for more flexibility and performance.
• Dependency Injection is built-in, whereas in Web Forms, it was typically implemented using third-party libraries.
• ASP.NET Core does not use the Global.asax file; instead, it uses a Startup class for configuration.

2. Setting Up the New Project

To start the migration, create a new ASP.NET Core project using Visual Studio or the .NET CLI:

    dotnet new webapp -n MyNewApp
    

This command creates a new ASP.NET Core web application.

3. Project Structure Changes

The project structure in ASP.NET Core is different from Web Forms. Here’s a typical structure:

    MyNewApp/
    ├── Controllers/
    ├── Models/
    ├── Views/
    ├── wwwroot/
    ├── appsettings.json
    └── Startup.cs
    

4. Configuring Services and Middleware

In ASP.NET Core, you configure services and middleware in the Startup.cs file. Here’s an example:

    public class Startup
    {
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllersWithViews();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                app.UseExceptionHandler("/Home/Error");
                app.UseHsts();
            }

            app.UseHttpsRedirection();
            app.UseStaticFiles();
            app.UseRouting();
            app.UseAuthorization();

            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllerRoute(
                    name: "default",
                    pattern: "{controller=Home}/{action=Index}/{id?}");
            });
        }
    }
    

5. Migrating Pages and Controls

ASP.NET Web Forms pages (.aspx) need to be converted to Razor views (.cshtml). For example, a simple Web Forms page:

    <!-- Default.aspx -->
    <asp:Label ID="lblMessage" runat="server" Text="Hello, World!" />
    

Would be converted to a Razor view like this:

    @* Default.cshtml *@
    <h1>Hello, World!</h1>
    

6. Handling Data Access

In ASP.NET Core, you can use Entity Framework Core for data access. Here’s how to set it up:

    public class MyDbContext : DbContext
    {
        public MyDbContext(DbContextOptions<MyDbContext> options) : base(options) { }

        public DbSet<Product> Products { get; set; }
    }
    

Configure the DbContext in Startup.cs:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddDbContext<MyDbContext>(options =>
            options.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
    }
    

7. Updating Authentication and Authorization

ASP.NET Core has a different approach to authentication and authorization. You can set it up in Startup.cs:

    public void ConfigureServices(IServiceCollection services)
    {
        services.AddAuthentication(CookieAuthenticationDefaults.AuthenticationScheme)
            .AddCookie(options =>
            {
                options.LoginPath = "/Account/Login";
            });
    }
    

8. Testing and Debugging

After migrating your application, thoroughly test all functionalities to ensure everything works as expected. Use the ASP.NET Core built-in logging and debugging tools to identify and fix any issues that arise during the migration process.

9. Conclusion

While migrating from ASP.NET Web Forms to ASP.NET Core can be a complex process, it offers an opportunity to modernize your application and take advantage of the latest features and performance improvements. By following the steps outlined in this guide, you can successfully transition your application to the new framework, ensuring a more maintainable and scalable solution for the future.