如何在ASP.NET MVC 6中为不同的环境注册不同的服务？

Question

What is the right way to configure services for different environments?

For example I want to add FakeService to services collection for DEV configuration and RealService for Release configuration.

public void ConfigureServices(IServiceCollection services)
{
    /* Need to check environment */
    services.AddSingleton<IService, FakeService>();
    ....
}

Answer 1

MVC 6 has a value that defines what environment it is, this can be set by the environment variable ASPNET_ENV. You can grab that value from IHostingEnvironment:

public void ConfigureServices(IServiceCollection services)
{
    var env = services.BuildServiceProvider().GetRequiredService<IHostingEnvironment>();
    if (env.IsDevelopment())
        Console.WriteLine("Development");
    else if (env.IsProduction())
        Console.WriteLine("Production");
    else if (env.IsEnvironment("MyCustomEnvironment"))
        Console.WriteLine("MyCustomEnvironment");
}

You can set the value in VS2015 on your project by Right-click > Properties > Debug > Environment Variables:

Here's some more info on configuring with environment variables .

Answer 2

It's just a matter of reading this from your configuration file, and making a decision in code accordingly:

bool isDev = Boolean.Parse(ConfigurationManager.AppSettings["IsDev"]);

if (isDev) {
    services.AddSingleton<IService, FakeService>();
} else {
    services.AddSingleton<IService, RealService>();
}

Another option is to use compiler directives:

if #DEBUG
    services.AddSingleton<IService, FakeService>();
#else
    services.AddSingleton<IService, RealService>();
#endif

Answer 3

While in debug configuration there is a DEBUG defined constant (automatically defined by Visual Studio) while there is no such constant defined for release mode.

if #DEBUG will work only for debug.

Check out the conditional methods https://msdn.microsoft.com/en-us/library/aa288458(v=vs.71).aspx

Use [Conditional("DEV")] or [Conditional("RELEASE")] before that method. It will execute when it matches mentioned configuration.

Answer 4

I'd suggest adding a layer of indirection. That is, use the IoC container to inject the appropriate version of the service:

services.AddService(container.Resolve<IMyServiceType>);

... of course you'll need to make sure the container returns the appropriate type for each environment.

I'm not sure you can do this with the default IoC container though; you might need to replace it with Ninject, Autofac, or whatever.