WebApi在调试时提供404；发布时有效 [英] WebApi giving 404 whilst debugging; works when published

问题描述

我有一个用.NET Core 2.2.6编写的控制台应用程序，它使用Kestrel托管简单的WebApi。

 公共类SettingsController：控制器
 {
 // 
 // GET：/ settings / 
 
 public string Index（）
 {
 return $ Hello world！控制器； 
} 
} 
  

如果我发布代码并运行可执行文件，我可以访问

其他一些可能有助于查明问题的代码：

 公共静态IWebHostBuilder CreateWebHostBuilder（string [] args）=> 
 WebHost.CreateDefaultBuilder（args）
 .ConfigureKestrel（（context，options）=> 
 {
 options.ListenAnyIP（310，listenOptions => 
 {
 listenOptions.Protocols = HttpProtocols.Http1; 
}）; 
}）
 .UseStartup< Startup>（）; 
 
公共类启动
 {
 public void ConfigureServices（IServiceCollection services）
 {
 services.AddMvc（）; 
} 
 
 public void Configure（IApplicationBuilder app，IHostingEnvironment env）
 {
 app.UseDefaultFiles（new DefaultFilesOptions（）
 {
 DefaultFileNames = new List< string>（）{ index.html} 
}）; 
 
 //返回静态文件并结束管道。 
 app.UseStaticFiles（new StaticFileOptions 
 {
 OnPrepareResponse = ctx => 
 {
 const int durationInSeconds = 60 * 60 * 24; 
 ctx。 Context.Response.Headers [HeaderNames.CacheControl] = 
 public，max-age = + durationInSeconds; 
} 
}）; 
 
 //使用Cookie政策中间件来符合欧盟通用数据
 //保护法规（GDPR）法规。 
 app.UseCookiePolicy（）; 
 
 //将MVC添加到请求管道。 
 app.UseMvcWithDefaultRoute（）; 
} 
} 
  

解决方案

一个非常相关的 GitHub问题，它解释了这里的情况。来自ASP.NET Core团队的Pranav K说：

MVC 2.1.0要求编译上下文可用。编译上下文告诉它库是否引用MVC，该MVC用作过滤器以跳过被认为不太可能具有控制器的程序集。 Microsoft.NET.Sdk没有设置< PreserveCompilationContext> true< / PreserveCompilationContext> ，这可以解释您为什么看到此消息。

这意味着您可以使用几种可行的解决方案来解决您遇到的问题：

1. 将 PreserveCompilationContext 属性添加到您的.csproj文件中，其值为 true ，如上所示。


2. 引用 Microsoft.NET.Sdk.Web 项目SDK，而不是 Microsoft.NET.Sdk 。

我不知道这两个选项之间有什么明显的区别，但是我会更新项目SDK实际上是您正在构建的Web项目。

I have a console application written in .NET Core 2.2.6 that is using Kestrel to host a simple WebApi.

public class SettingsController : Controller
{
    // 
    // GET: /settings/

    public string Index()
    {
        return $"Hello world! controller";
    }
}

If I publish the code and run the executable, I can visit http://127.0.0.1:310/settings and see the expected "Hello world! controller". However, if I debug (or even open in Release mode) from inside Visual Studio 2019, the same URL throws a 404 exception.

Some other code that might help pinpoint the problem:

public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
    WebHost.CreateDefaultBuilder(args)
        .ConfigureKestrel((context, options) =>
        {
            options.ListenAnyIP(310, listenOptions =>
            {
                listenOptions.Protocols = HttpProtocols.Http1;
            });
        })
        .UseStartup<Startup>();

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

    public void Configure(IApplicationBuilder app, IHostingEnvironment env)
    {
        app.UseDefaultFiles(new DefaultFilesOptions()
        {
            DefaultFileNames = new List<string>() { "index.html" }
        });

        // Return static files and end the pipeline.
        app.UseStaticFiles(new StaticFileOptions
        {
            OnPrepareResponse = ctx =>
            {
                const int durationInSeconds = 60 * 60 * 24;
                ctx.Context.Response.Headers[HeaderNames.CacheControl] =
                    "public,max-age=" + durationInSeconds;
            }
        });

        // Use Cookie Policy Middleware to conform to EU General Data 
        // Protection Regulation (GDPR) regulations.
        app.UseCookiePolicy();

        // Add MVC to the request pipeline.
        app.UseMvcWithDefaultRoute();
    }
}

解决方案

There's a very relevant GitHub issue that explains what's going on here. Pranav K from the ASP.NET Core team says:

MVC 2.1.0 requires compilation context to be available. Compilation context tells it if a library references MVC which is used as a filter to skip assemblies that are deemed unlikely to have controllers. Microsoft.NET.Sdk does not set <PreserveCompilationContext>true</PreserveCompilationContext> which would explain why you're seeing this.

This means there's a couple of working solutions to the problem you're seeing:

1. Add the PreserveCompilationContext property to your .csproj file with a value of true, as shown above.
2. Reference the Microsoft.NET.Sdk.Web project SDK instead of Microsoft.NET.Sdk.

I don't know of any perceivable difference between these two options, but I would just update the project SDK given that it is in fact a Web project you're building.

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