How to read appsettings.json in my _layout.chtml

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