Microsoft.Extensions.PlatformAbstractions has been removed

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In ASP.NET Core 2.0 we are removing the Microsoft.Extensions.PlatformAbstractions package as it is no longer necessary to maintain this abstraction. Consumers of this package will need to replace their use of these APIs with the standard .NET APIs as follows:

Microsoft.Extensions.PlatformAbstractions	Equivalent .NET API
ApplicationEnvironment.ApplicationBasePath	System.AppContext.BaseDirectory or System.AppDomain.CurrentDomain.BaseDirectory
ApplicationEnvironment.ApplicationName	System.Reflection.Assembly.GetEntryAssembly().GetName().Name or System.AppDomain.CurrentDomain.SetupInformation.ApplicationName
ApplicationEnvironment.ApplicationVersion	System.Reflection.Assembly.GetEntryAssembly().GetName().Version
ApplicationEnvironment.RuntimeFramework	System.Reflection.Assembly.GetEntryAssembly().GetCustomAttribute<TargetFrameworkAttribute>().FrameworkName or System.AppDomain.CurrentDomain.SetupInformation.TargetFrameworkName

See aspnet/PlatformAbstractions#50 for more detail or to discuss this change.

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Note: As part of this change, you could encounter the following error if you build your WebHost by injecting IStartup directly into the DI container, rather than calling .UseStartup or .Configure:

Unhandled Exception: System.ArgumentException: A valid non-empty application name must be provided.
Parameter name: applicationName
   at Microsoft.AspNetCore.Hosting.Internal.HostingEnvironmentExtensions.Initialize(IHostingEnvironment hostingEnvironment, String applicationName, String contentRootPath, WebHostOptions options)
   at Microsoft.AspNetCore.Hosting.WebHostBuilder.BuildCommonServices(AggregateException& hostingStartupErrors)
   at Microsoft.AspNetCore.Hosting.WebHostBuilder.Build()
   at ConsoleApp11.Program.Main(String[] args) in C:\Users\dfowler\documents\visual studio 2017\Projects\ConsoleApp11\ConsoleApp11\Program.cs:line 11

This occurs because we need to get the name of the application. Previously, we used some heuristics to detect it, but we removed some of them in 2.0. In the scenario above, where IStartup is manually injected into the container, add the following call to your WebHostBuilder set-up sequence:

WebHost.CreateDefaultBuilder(args)
    // ... other Web Host configuration calls
    .UseSetting(WebHostDefaults.ApplicationKey, "[Application Name]")

NOTE: This is only required in 2.0 and only when you do NOT call .UseStartup or .Configure

See aspnet/Hosting#1137 for further info.