英文:
IHostEnvironment.EnvironmentName VS Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT")
问题
在一个使用.NET 6构建的ASP.NET Core Web API应用程序中，IHostEnvironment.EnvironmentName 和 Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT") 是否始终相同？如果不相同，它们在什么情况下会有差异？
要详细说明一下，我的问题是关于.NET注入到Startup构造函数中的IHostEnvironment实例。类似于这样的内容：Startup(IHostEnvironment env)。
英文:
In an ASP.NET Core Web API application, built using .NET 6, is IHostEnvironment.EnvironmentName and Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT") always the same? If not, under what circumstances can they differ?
To elaborate a bit, my question is about the IHostEnvironment instance which is injected in Startup constructor by the .NET. Something like this Startup(IHostEnvironment env).
答案1
得分: 1
请参阅此处，了解关于环境确定方式的完整文档。
简而言之，环境是通过读取 DOTNET_ENVIRONMENT 和 ASPNETCORE_ENVIRONMENT 两者来确定的。根据你使用的构建器，其中一个可能会优先于另一个。
当使用 WebApplicationBuilder 时，DOTNET_ENVIRONMENT 的值会覆盖 ASPNETCORE_ENVIRONMENT。对于其他主机，比如 ConfigureWebHostDefaults 和 WebHost.CreateDefaultBuilder，ASPNETCORE_ENVIRONMENT 有更高的优先级。
另外，也可以通过命令行参数来提供环境，例如：dotnet run --environment Production。
最后，还可以将环境作为构建器的参数提供：
WebApplication.CreateBuilder(new WebApplicationOptions
{
EnvironmentName = Environments.Staging
});
尽管我必须说我从未不得不这样做过。总的来说，考虑到可能的信息来源有多种，最好不要读取环境变量，而是使用 IHostingEnvironment。
最后一点，环境默认为 Production，除非你明确使用默认值，否则你的环境变量不会设置为该值。
英文:
Please see here for the full documentation on how the environment is determined
The gist of it is that both DOTNET_ENVIRONMENT and ASPNETCORE_ENVIRONMENT are read to determine the environment. Depending on which builder you use, one can take precedence over the other.
> The DOTNET_ENVIRONMENT value overrides ASPNETCORE_ENVIRONMENT when WebApplicationBuilder is used. For other hosts, such as ConfigureWebHostDefaults and WebHost.CreateDefaultBuilder, ASPNETCORE_ENVIRONMENT has higher precedence.
Alternatively, it is also possible to provide the environment as command line parameter as such: dotnet run --environment Production
Finally, it is also possible to provide the environment as an argument to the builder itself:
WebApplication.CreateBuilder(new WebApplicationOptions
{
EnvironmentName = Environments.Staging
});
though I have to say I've never had to do that. All in all, considering how many possible sources there are, it's definitely not a great idea to read the environment variable instead of using the IHostingEnvironment.
One last thing. The environment defaults to Production, which your environment variable won't do unless you explicitly use a default.
答案2
得分: 1
IHostEnvironment.EnvironmentName 和 Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT") 总是相同吗？
在深入讨论您的主要问题之前，需要简要介绍一下，但我保证这会让您对您感兴趣的内容有所启发。
IHostEnvironment.EnvironmentName：
通常，IHostEnvironment.EnvironmentName 是 asp.net core 6 之前的版本的一部分，它源自 IHostEnvironment 接口，它通过读取 launchSettings.json 中的信息来提供有关应用程序正在运行的托管环境的信息，如下所示：
Environment.GetEnvironmentVariable()：
从 .NET 6 开始，不再使用 IHostEnvironment.EnvironmentName，取而代之的是 Environment.GetEnvironmentVariable()，它也从 launchSettings.json 中检索环境变量名称，这是从 Environment 静态类派生出来的，如下所示：
因此，IHostEnvironment.EnvironmentName 适用于 .NET 6 之前的版本，而 Environment.GetEnvironmentVariable() 适用于 .NET 6 及以后的版本，两者都提供了应用程序环境信息，例如开发环境、生产环境或预发布环境。
如果它们不相同，那么在什么情况下它们会有差异？
IHostEnvironment.EnvironmentName 中的 DOTNET_ENVIRONMENT：
实际上，根据 DOTNET_ENVIRONMENT 和 ASPNETCORE_ENVIRONMENT，我们可能会得到不同的结果。因为在使用 asp.net core 版本早于 6 的情况下，DOTNET_ENVIRONMENT 的值会覆盖 ASPNETCORE_ENVIRONMENT，因此，您仍然可以准确获取环境变量名称，如下所示：
Environment.GetEnvironmentVariable() 中的 DOTNET_ENVIRONMENT：
然而，在 asp.net core 6 及更高版本中，与早于 asp.net core 6 的情况不同，它不会按预期运行。因为 ASPNETCORE_ENVIRONMENT 优先级高于 DOTNET_ENVIRONMENT，您将得到完全不同的结果。对于 DOTNET_ENVIRONMENT，您将获得 null EnvironmentVariable，如下所示：
注意： 总结一下，它们都适用于在运行时获取应用程序环境变量信息。但根据 DOTNET_ENVIRONMENT 的优先级，它们的值会有所不同。如果您仍然想要了解更多详细信息，可以查看我们的官方文档。
英文:
> IHostEnvironment.EnvironmentName and
> Environment.GetEnvironmentVariable("DOTNET_ENVIRONMENT") always the
> same?
Before jumping into your main question it needs a brief background but I promise it would enlight you what you are curious about.
IHostEnvironment.EnvironmentName:
Generally, IHostEnvironment.EnvironmentName of asp.net core older than 6 which is derived from IHostEnvironment Interface that returns us information about the hosting environment an application is running in by reading information from launchSettings.json as you can see below:
Environment.GetEnvironmentVariable():
From dotnet 6 IHostEnvironment.EnvironmentName not longer using and it replaced by Environment.GetEnvironmentVariable() which also Retrieves environment variable names from launchSettings.json that is derived from Environment static class as you can see below:
Therefore, IHostEnvironment.EnvironmentName older than dotnet6 and Environment.GetEnvironmentVariable() of later than dotnet6 both provides us the information of application environment. For instance, whether its dev, prod or stage.
> If not, under what circumstances can they differ?
DOTNET_ENVIRONMENT In IHostEnvironment.EnvironmentName:
Actually, Depending on DOTNET_ENVIRONMENT and ASPNETCORE_ENVIRONMENT we may experience divergent result. Because DOTNET_ENVIRONMENT value overrides ASPNETCORE_ENVIRONMENT when you would used in asp.net core version older than 6 as it overrides; Thus, you still can get the environment variable name exactly. As you can see below:
DOTNET_ENVIRONMENT In Environment.GetEnvironmentVariable():
However, it doesn't act accrdingly in asp.net core 6 and later version unlike older than asp.net core 6. Because ASPNETCORE_ENVIRONMENT has higher precedence over DOTNET_ENVIRONMENT and you would ended up completely different result. For DOTNET_ENVIRONMENT you would get null EnvironmentVariable which you can see below:
Note: In summary, they both works for getting application environment varibale information while runnning. But denpending on DOTNET_ENVIRONMENT precedence their value differ. If you still would like to know more details on it you could check our official document here
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