How to read appsettings.json in my _layout.chtml

I cannot seem to figure out how to read values from the appsettings.json in my _Layout.chtml file.

Is it not just available, something like this? @Configuration["ApplicationInsights:InstrumentationKey"]

I created a new MVC project using razor pages.

fyi, i'm an mvc newbee - code samples help a lot.

In .net core mvc you can inject the configuration by adding the following two lines at the top of your view:

@using Microsoft.Extensions.Configuration
@inject IConfiguration Configuration

You can then access the value like this:

@Configuration.GetSection("ApplicationInsights")["InstrumentationKey"]

If you use the options pattern you can inject them into your view like this:

@using Microsoft.Extensions.Options
@inject IOptions<ApplicationInsightsOptions> 
ApplicationInsightsOptionsAccessor
@
{
   var instrumentationKey = 
        ApplicationInsightsOptionsAccessor.Value.InstrumentationKey;
}

Options pattern in ASP.NET Core

Using ActionFilters you can interrupt the request and add the configuration variables maybe to the ViewBag so it becomes accessible from the views or from the _Layout.cshtml File.

For example, if the following configuration section is inside your appsettings.json

{
    "MyConfig": {
        "MyValue": "abc-def"
    }
}

In the code MyConfig.cs would be:

public class MyConfig
{
    public string MyValue{ get; set; }
}

First create a very simple ActionFilter which derives from IAsyncActionFilter as following :

public class SampleActionFilter : IAsyncActionFilter
{
    private MyConfig _options;
    public SampleActionFilter(IConfiguration configuration)
    {

        _options = new MyConfig();
        configuration.Bind(_options);
    }

    public async Task OnActionExecutionAsync(ActionExecutingContext context, ActionExecutionDelegate next)
    {
        ((Microsoft.AspNetCore.Mvc.Controller)context.Controller).ViewBag.MyConfig = _options;
        await next();
    }
}

Later in the Startup.ConfigureServices method change services.AddMvc to the following:

public void ConfigureServices(IServiceCollection services)
{

    //..........

    services.AddMvc(options=>
    {
        options.Filters.Add(new SampleActionFilter(
            Configuration.GetSection("MyConfig")
        ));
    });

    //..........

}

To access the values just simply in the _Layout.cshtml or other view you can type:

@ViewBag.MyConfig.MyValue