.Net Core 2.2 迁移 .Net Core 3.1

目标：已搭建完成的.Net Core 2.2项目 迁移为 .Net Core 3.1版本项目，并可正常运行

1、全部项目右键选中【属性】——>应用程序——>目标框架 .Net Core 2.2 改成  .Net Core 3.1

2、项目启动 Program.cs 更改

.Net Core 2.2启动方式：

public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>();

.Net Core 3.1 启动方式：

public static void Main(string[] args)
        {
            CreateHostBuilder(args).Build().Run();
        }

        public static IHostBuilder CreateHostBuilder(string[] args) =>
           Host.CreateDefaultBuilder(args)
            .ConfigureWebHostDefaults(webBuilder =>
            {
                webBuilder.UseStartup<Startup>();
            });

3、Startup.cs 更改

.Net Core 2.2 :

public void ConfigureServices(IServiceCollection services)
        {
             services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
        }

        public void Configure(IApplicationBuilder app, IHostingEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseMvc();
        }

.Net Core 3.1

public void ConfigureServices(IServiceCollection services)
        {
            services.AddControllers();
        }

        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }

            app.UseRouting();
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }

4、更新全部Nuget包至最新

 

简单的项目，这样更改，就能够正常运行啦！

官网迁移文档：https://docs.microsoft.com/zh-cn/aspnet/core/migration/22-to-30?view=aspnetcore-3.1&tabs=visual-studio

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