AppConfig Feature Management with Azure Functions

FeatureManagementConfig.cs

namespace FunctionAppWithFeatureManagement
{
    public static class FeatureManagementConfig
    {
        public static string ConnectionStringSetting => "FeatureConfigConnectionString";
        public static string FeaturePrefix => "FuncApp-*";
        public static string FuncAppFeatureA => "FuncApp-FeatureA";
    }
}

FunctionAppWithFeatureManagement.csproj

<Project Sdk="Microsoft.NET.Sdk">
  <PropertyGroup>
    <TargetFramework>netcoreapp3.1</TargetFramework>
    <AzureFunctionsVersion>v3</AzureFunctionsVersion>
  </PropertyGroup>
  <ItemGroup>
    <PackageReference Include="Microsoft.Azure.Functions.Extensions" Version="1.1.0" />
    <PackageReference Include="Microsoft.Extensions.Configuration.AzureAppConfiguration" Version="4.0.0" />
    <PackageReference Include="Microsoft.FeatureManagement" Version="2.2.0" />
    <PackageReference Include="Microsoft.NET.Sdk.Functions" Version="3.0.11" />
  </ItemGroup>
  <ItemGroup>
    <None Update="host.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
    </None>
    <None Update="local.settings.json">
      <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
      <CopyToPublishDirectory>Never</CopyToPublishDirectory>
    </None>
  </ItemGroup>
</Project>

HttpTriggerFeatureA.cs

using System.Threading.Tasks;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.WebJobs;
using Microsoft.Azure.WebJobs.Extensions.Http;
using Microsoft.AspNetCore.Http;
using Microsoft.Extensions.Logging;
using Microsoft.FeatureManagement;
using Microsoft.Extensions.Configuration.AzureAppConfiguration;

namespace FunctionAppWithFeatureManagement
{
    public class HttpTriggerFeatureA
    {
        private readonly IFeatureManagerSnapshot _featureManagerSnapshot;
        private readonly IConfigurationRefresher _configurationRefresher;

        public HttpTriggerFeatureA(IFeatureManagerSnapshot featureManagerSnapshot, IConfigurationRefresher configurationRefresher)
        {
            _featureManagerSnapshot = featureManagerSnapshot;
            _configurationRefresher = configurationRefresher;
        }

        [FunctionName(nameof(HttpTriggerFeatureA))]
        public async Task<IActionResult> Run(
            [HttpTrigger(AuthorizationLevel.Function, "get", Route = null)] HttpRequest req,
            ILogger log)
        {
            await _configurationRefresher.TryRefreshAsync();

            string responseMessage;
            if (await _featureManagerSnapshot.IsEnabledAsync(FeatureManagementConfig.FuncAppFeatureA))
            {
                responseMessage = $"{FeatureManagementConfig.FuncAppFeatureA} is enabled.";
            }
            else
            {
                responseMessage = $"{FeatureManagementConfig.FuncAppFeatureA} is disabled.";
            }

            return new OkObjectResult(responseMessage);
        }
    }
}

StartUp.cs

using FunctionAppWithFeatureManagement;
using Microsoft.Azure.Functions.Extensions.DependencyInjection;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.Configuration.AzureAppConfiguration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.FeatureManagement;
using Microsoft.FeatureManagement.FeatureFilters;
using System;

[assembly: FunctionsStartup(typeof(StartUp))]
namespace FunctionAppWithFeatureManagement
{

    public class StartUp : FunctionsStartup
    {
        public override void Configure(IFunctionsHostBuilder builder)
        {
            IConfigurationRefresher configurationRefresher = null;

            IConfigurationRoot configuration = new ConfigurationBuilder()
                .AddAzureAppConfiguration(options =>
               {
                   options.Connect(Environment.GetEnvironmentVariable(FeatureManagementConfig.ConnectionStringSetting))
                    .Select(FeatureManagementConfig.FeaturePrefix)
                    .ConfigureRefresh(refreshOptions => 
                        refreshOptions
                        .Register(FeatureManagementConfig.FuncAppFeatureA, refreshAll: true)
                        .SetCacheExpiration(TimeSpan.FromSeconds(10)))
                    .UseFeatureFlags();
                   configurationRefresher = options.GetRefresher();
               })
               .Build();

            builder.Services.AddFeatureManagement(configuration);
            builder.Services.AddSingleton<IConfigurationRefresher>(configurationRefresher);
        }
    }
}