相关疑难解决方法(0)

我将具有 2 个类库和一个 Mvc 项目的项目从 2.2 升级到 MVC Core 3.0 \n在本页 \n在此处输入链接描述

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1. 改变.net <TargetFramework>netcoreapp3.0</TargetFramework>

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   2.这样改

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   <ItemGroup>\n<!--<PackageReference Include="Microsoft.AspNetCore.App" />-->\n<!--<PackageReference Include="Microsoft.AspNetCore.Identity" Version="2.2.0" />-->\n<PackageReference Include="Microsoft.AspNetCore.Identity.UI" Version="3.0.0" />\n<!--<PackageReference Include="Microsoft.AspNetCore.Razor.Design" Version="2.2.0" PrivateAssets="All" />-->\n<PackageReference Include="Microsoft.VisualStudio.Web.CodeGeneration.Design" Version="3.0.0" />\n</ItemGroup>

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   3.我的satrtup.cs

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   `
   \n app.UseHttpsRedirection();\n app.UseStaticFiles();\n app.UseDefaultFiles();\n app.UseCookiePolicy();

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       app.UseRouting();\n\n    app.UseAuthorization();\n\n    app.UseEndpoints(endpoints =>\n    {\n        endpoints.MapRazorPages();\n    });`\n

   Run Code Online (Sandbox Code Playgroud)
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2. 我的程序.cs

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   public static void Main(string[] args)\n {\n CreateHostBuilder(args).Build().Run();\n }\n public static IHostBuilder CreateHostBuilder(string[] args) =>\n Host.CreateDefaultBuilder (args)\n .ConfigureWebHostDefaults(webBuilder =>\n {\n webBuilder.UseStartup();\n });

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但是当我运行我的项目时出现此错误 …