将.NET Framework 4.5的Web API 2.0迁移至.NET Core 2.1.4的疑问求助

Hey there, let's break this down clearly for you.

First off, the method you found—changing the project's target framework to .NET Framework 7.0 via project properties—won't help you deploy to Linux at all. Here's why: .NET Framework, even the latest 7.0 version, is still a Windows-only runtime. Upgrading to it just moves your project to a newer Windows-exclusive framework, but it won't give you cross-platform compatibility with Linux. So that approach is not feasible for your goal.

Since you need to get your Web API 2.0 (built on .NET Framework 4.5) running on Linux, here's a step-by-step, reliable approach:

1. Audit Your Project's Dependencies & Compatibility #

First, map out all parts of your existing project that might not work with .NET Core 2.1:

• Use Visual Studio's Portability Analyzer to scan your project. It will flag APIs, NuGet packages, and Windows-specific code (like System.Drawing, Microsoft.Win32 classes, or IIS-only features) that aren't supported in .NET Core.
• Check your NuGet packages: Some have .NET Core-compatible versions, others don't. For example, Newtonsoft.Json works fine in .NET Core 2.1, but older Windows-only libraries may need replacement.

2. Create a Fresh .NET Core 2.1 Web API Project #

Don't try to modify your existing project directly—starting fresh avoids messy compatibility leftovers:

• Open Visual Studio, create a new "ASP.NET Core Web API" project, and select .NET Core 2.1 as the target framework.
• Copy over your core business logic: controllers, models, service classes, and other non-Windows-specific code to the new project. Leave behind any web.config settings or Windows-only utility code.

3. Migrate Configuration & Dependency Injection #

Web API 2.0 and .NET Core handle these differently:

• Routing: Replace WebApiConfig.cs with routing setup in the new project's Startup.cs Configure method, using app.UseMvc() to define routes.
• Dependency Injection: .NET Core has a built-in DI system. Register your services in Startup.cs's ConfigureServices method (e.g., services.AddScoped<IMyService, MyService>()). If you used third-party containers like Unity or Autofac, you can integrate them with .NET Core's DI system.
• Configuration: Swap web.config for appsettings.json, and use the IConfiguration interface to read settings instead of ConfigurationManager.

4. Migrate Data Access #

If you used Entity Framework 6, you'll need to switch to Entity Framework Core 2.1:

• EF Core has different API syntax than EF6—adjust your DbContext setup, query logic, and migrations accordingly.
• For ADO.NET code, most will work as-is, but make sure you're using .NET Core-compatible database drivers (like Microsoft.Data.SqlClient for SQL Server).

5. Test (Even Without a Linux Host) #

You can validate your project before deploying to Linux:

• Run the project locally using Kestrel (the default .NET Core web server) to ensure all endpoints work as expected.
• Use Docker on Windows to simulate a Linux environment: Add Docker support to your project, select a Linux base image, and run the container to catch cross-platform bugs early.

6. Deploy to Linux #

Once testing passes, deploy your project:

• Generate a Linux-specific publish package with the command: dotnet publish -c Release -r linux-x64
• Deploy options:
  • Run the published DLL directly on Linux with dotnet YourProject.dll
  • Use Nginx as a reverse proxy to handle incoming traffic, and systemd to manage the API as a background service.

A Quick Note on .NET Versions #

While you specified .NET Core 2.1.4, keep in mind it reached end-of-support in August 2021. If possible, consider migrating to a newer long-term support (LTS) version like .NET 6 or .NET 8—they offer better performance, more features, and ongoing security updates, with a similar deployment workflow for Linux.

内容的提问来源于stack exchange，提问作者Pavan