Adding the Key Vault config provider in Asp.Net Core

Example.csproj

<Project Sdk="Microsoft.NET.Sdk.Web">

  <PropertyGroup>
    <TargetFramework>netcoreapp3.0</TargetFramework>
  </PropertyGroup>

  <ItemGroup>
    <PackageReference Include="Microsoft.Extensions.Configuration.AzureKeyVault" Version="3.0.0" />
  </ItemGroup>
  
</Project>

Program.cs

using Microsoft.AspNetCore;
using Microsoft.AspNetCore.Hosting;
using Microsoft.Extensions.Configuration;

namespace Example
{
    public class Program
    {
        public static void Main(string[] args)
        {
            CreateWebHostBuilder(args).Build().Run();
        }

        public static IWebHostBuilder CreateWebHostBuilder(string[] args) =>
            WebHost.CreateDefaultBuilder(args)
                .UseStartup<Startup>()
                .ConfigureAppConfiguration((context, configBuilder) =>
                {                    
                    // first we need to build the config object so we can grab the key vault url that 
                    // was passed in another way, such as an environment variable or appsettings.json
                    var config = configBuilder.Build();         
                    
                    configBuilder.AddAzureKeyVault(config["KeyVaultUrl"]);
                });
    }
}