When starting up a plain dotnet new mvc app, Environment.GetEnvironmentVariables() is called three times, once from HostBuilder.BuildAppConfiguration(), once from HostBuilder.BuildHostConfiguration(), and once from Microsoft.AspNetCore.Host.GenericWebHostBuilder, resulting in the environment variables being parsed multiple times and in three times as many strings being created as is really needed:

At least the first two are both called from the same method, HostBuilder.Build:

It'd be nice if the call could be made once and the results used for the various calls. (It's more challenging / problematic for Environment.GetEnvironmentVariables() to cache, but we could look at that, too, if necessary.)

Related to #44598