public class Startup
  {
    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
      if (env.IsDevelopment())
      {
      }

      app.Run(async (context) =>
      {
        await context.Response.WriteAsync(
          $"EnvironmentName: {env.EnvironmentName},IsDevelopment: {env.IsDevelopment()}"
        );
      });
    }
  }

   public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
      env.EnvironmentName = "test";

      if (env.IsDevelopment())
      {
        //TODO
      }else if (env.IsEnvironment("text"))
      {
        //TODO
      }

      app.Run(async (context) =>
      {
        await context.Response.WriteAsync(
          $"EnvironmentName: {env.EnvironmentName},IsDevelopment: {env.IsDevelopment()}"
        );
      });
 }

    public static IHostBuilder CreateHostBuilder(string[] args) =>
      Host.CreateDefaultBuilder(args)
        .ConfigureAppConfiguration((hostContext, config) =>
        {
          var env = hostContext.HostingEnvironment;
          config.SetBasePath(Path.Combine(env.ContentRootPath, "Configuration"))
            .AddJsonFile(path: "settings.json", optional: false, reloadOnChange: true)
            .AddJsonFile(path: $"settings.{env.EnvironmentName}.json", optional: true, reloadOnChange: true);
        })
        .ConfigureWebHostDefaults(webBuilder =>
        {
          webBuilder.UseStartup<Startup>();
        });

<"1.0" encoding="utf-8""aspNetCore" path="*" verb="*" modules="AspNetCoreModule" resourceType="Unspecified" />
  </handlers>
  <aspNetCore processPath="dotnet" arguments=".\Demo.dll" stdoutLogEnabled="false" stdoutLogFile=".\logs\stdout">
   <environmentVariables>
    <environmentVariable name="ASPNETCORE_ENVIRONMENT" value="Test" />
   </environmentVariables>
  </aspNetCore>
 </system.webServer>
</configuration>

{
  "version": "0.1.0",
  "configurations": [
    {
      "name": ".NET Core Launch (web)",
      "type": "coreclr",
      "env": {
        "ASPNETCORE_ENVIRONMENT": "Development"
      }
    }
  ]
}

 "profiles": {
  "IIS Express": {
   "commandName": "IISExpress",
   "launchBrowser": true,
   "environmentVariables": {
    "ASPNETCORE_ENVIRONMENT": "Test"
   }
  },
  }