How to access IHostingEnvironment, ContentRoot inside Program.cs Main method?

[tekbyts]

This is my use case:

Download appsettings.json from an external trust store and place it inside the web application project root directory.
I should do this inside Program.cs -> Main method as the first thing to be done before CreateWebHostBuilder
In order to achieve that, i need access to IHostingEnvironment.ContentRootPath

Below is the code: i can declare a variable inside the Main method of type IHostingEnvironment but i am not sure what should i initialize it with

public static void Main(string[] args)
{
    IHostingEnvironment env;
}

[davidfowl]

You can't access it inside of main. The host needs to be built before you can access anything there. The best you can do is set the content root.

[Tratcher]

            var host = new HostBuilder();
            host.ConfigureAppConfiguration((hostContext, config) =>
            {
                var hostEnvironment = hostContext.HostingEnvironment;
                // TODO: Copy the appsettings.json file...

                config.AddJsonFile("AppSettings.json", optional: false);
            });

The downside of this approach is that you can't use Host.CreateDefaultBuilder due to ordering issues. However, you can copy as much code for that from here as you need:
https://github.com/dotnet/runtime/blob/ac3595e47432b728ddccabdc280692ac0e9405f7/src/libraries/Microsoft.Extensions.Hosting/src/Host.cs#L56

[davidfowl]

That doesn't run until Build is called... I'm not 100% sure how this would work.

[Tratcher]

Sure, the download would happen during Build. As long as it happens before AddJsonFile is called it should work in this scenario.

[Tratcher]

Alternatively, you could do the download first into a temp location, and then copy it to the app on that TODO line.

Of course you could change the premise of the problem and write a config provider instead. No need to mess with the appsetting.json file. It would be something like the KeyVault provider.
https://github.com/dotnet/extensions/blob/release/3.1/src/Configuration/Config.AzureKeyVault/src/AzureKeyVaultConfigurationExtensions.cs

[davidfowl]

That's preferred I think.

[tekbyts]

Can you please provide a code sample?

…

On Tue, Sep 8, 2020 at 5:57 PM Chris Ross ***@***.***> wrote: What about doing it inside of a IHostBuilder.ConfigureAppConfiguration callback? As long as you registered that callback early enough... — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#25695 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AKHUPP2SOHZY7P67OO4MBF3SE2SFLANCNFSM4RAH753A> .