宿主环境来自ASPNET_ENV环境变量，在启动过程中使用IHostingEnvironment可用。IsEnvironment扩展方法，或IsDevelopment或IsProduction中相应的方便方法之一。在Startup()中保存你需要的东西，或者在ConfigureServices调用中保存:

var foo = Environment.GetEnvironmentVariable("ASPNET_ENV");

在. net Core 2.0 MVC app / Microsoft.AspNetCore.All v2.0.0中，你可以有@vaindil所描述的特定于环境的启动类，但我不喜欢这种方法。

你也可以在StartUp构造函数中注入IHostingEnvironment。不需要将环境变量存储在Program类中。

public class Startup
{
    private readonly IHostingEnvironment _currentEnvironment;
    public IConfiguration Configuration { get; private set; }

    public Startup(IConfiguration configuration, IHostingEnvironment env)
    {
        _currentEnvironment = env;
        Configuration = configuration;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        ......

        services.AddMvc(config =>
        {
            // Requiring authenticated users on the site globally
            var policy = new AuthorizationPolicyBuilder()
                .RequireAuthenticatedUser()
                .Build();
            config.Filters.Add(new AuthorizeFilter(policy));

            // Validate anti-forgery token globally
            config.Filters.Add(new AutoValidateAntiforgeryTokenAttribute());

            // If it's Production, enable HTTPS
            if (_currentEnvironment.IsProduction())      // <------
            {
                config.Filters.Add(new RequireHttpsAttribute());
            }            
        });

        ......
    }
}

从ASP开始。NET Core 3.0中，从ConfigureServices和Configure中访问环境变量要简单得多。

只需将IWebHostEnvironment注入到启动构造函数本身。像这样…

public class Startup
{
    public Startup(IConfiguration configuration, IWebHostEnvironment env)
    {
        Configuration = configuration;
        _env = env;
    }

    public IConfiguration Configuration { get; }
    private readonly IWebHostEnvironment _env;

    public void ConfigureServices(IServiceCollection services)
    {
        if (_env.IsDevelopment())
        {
            //development
        }
    }

    public void Configure(IApplicationBuilder app)
    {
        if (_env.IsDevelopment())
        {
            //development
        }
    }
}

参考:https://learn.microsoft.com/en - us/aspnet/core/fundamentals/environments?view=aspnetcore - 3.0 # inject-iwebhostenvironment-into-the-startup-class

对于blazor服务器应用程序，我这样做:Startup.cs直接在命名空间声明add

namespace myProjectName.Server

public static class myGlobals

{
    public static bool isDevelopment = true;
}

Startup.cs找到Configure方法和env. cs的现有检查。并将上面声明的静态IsDevelopment设置为true或false。

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
           myGlobals.isDevelopment = true;
        }
        else false

在ApplicationUser中初始化数据库连接或其他任何地方

        if (myGlobals.isDevelopment)
        {

如果你需要在你的代码库中某个不容易访问IHostingEnvironment的地方测试这个，另一个简单的方法是这样做的:

bool isDevelopment = Environment.GetEnvironmentVariable("ASPNETCORE_ENVIRONMENT") == "Development";

由于还没有完整的复制和粘贴解决方案，基于Joe Audette的回答:

public IWebHostEnvironment Environment { get; }

public Startup(IWebHostEnvironment environment, IConfiguration configuration)
{
   Environment = environment;
   ...
}

public void ConfigureServices(IServiceCollection services)
{
   if (Environment.IsDevelopment())
   {
       // Do something
   }else{
       // Do something
   }
   ...
}