Access IApplicationEnvironment in ConfigureServices

Question

In my ConfigureServices method I want to read a file (in my case a certificate used for signing tokens, but it could be any file necessary for setting up services). Therefore I need to know the ApplicationBasePath from IApplicationEnvironment.

Currently I solve the problem by getting the IApplicationEnvironment service like this:

public void ConfigureServices(IServiceCollection services)
{
    ...
    string basePath;
    var serviceProvider = services.BuildServiceProvider();
    try
    {
        basePath = serviceProvider.GetRequiredService<IApplicationEnvironment>().ApplicationBasePath;
    }
    finally
    {
        (serviceProvider as IDisposable)?.Dispose();
    }
    ...
}

This approach works but I am not sure if that's the right approach. So my questions are:

1. Is there a better way to read a file in ConfigureServices?
2. Is there a better way to get the application base path in ConfigureServices?
3. If my approach is correct, do I handle IDisposable correctly?

Answer 1

The runtime allows dependency injection in the constructor of the Startup class:

public class Startup
{
    private readonly IApplicationEnvironment _appEnv;

    public Startup(IApplicationEnvironment appEnv)
    {
        _appEnv = appEnv;
    }

    public void ConfigureServices(IServiceCollection services)
    {
        string basePath = _appEnv.ApplicationBasePath;
    }
}

Answer 2

How to obtain an IApplicationEnvironment instance following the release of DNX 1.0.0-rc1-15996

To obtain a reference to an implementer of the IApplicationEnviroment interface you can use PlatformServices.Default.Application.

The following example shows this in the context of a project's Startup.cs file:

using Microsoft.Extensions.PlatformAbstractions;

namespace MyWebApp
{
    public class Startup
    {       
        private IApplicationEnvironment _appEnv { get; set; }

        public Startup(IHostingEnvironment env)
        {
            // Set up configuration sources.
            var builder = new ConfigurationBuilder()                
                .AddJsonFile("appsettings.json")
                .AddJsonFile($"appsettings.{env.EnvironmentName}.json", optional: false);

            if (env.IsDevelopment())
            {
                // For more details on using the user secret store see http://go.microsoft.com/fwlink/?LinkID=532709
                builder.AddUserSecrets();
            }

            builder.AddEnvironmentVariables();          
            Configuration = builder.Build();

            // obtain IApplicationEnvironment instance
            _appEnv = PlatformServices.Default.Application;

        }
...

The following line shows how to use that instance to obtain the application's base path:

 string basepath = _appEnv.ApplicationBasePath

References:

1. Refactoring DNX not to inject into Program constructors #2990
2. IApplicationEnvironment no longer injected in DNX command