How can i implement feature flag using Azure App Configuration for MVC project in .Net Framework

Question

1. "I am interested in utilizing the Azure App Configuration feature manager to implement a feature flag."
2. "While I have come across documentation from Microsoft that explains how to implement a feature flag for a console application (https://learn.microsoft.com/en-us/azure/azure-app-configuration/quickstart-feature-flag-dotnet), I still find myself uncertain about its implementation for an MVC project in the .NET Framework."
3. "I would appreciate guidance on implementing a feature flag for a web application in the .NET Framework. It would be great if you could provide a solution or point me towards relevant documentation for reference."

Answer 1

Prasanna Venkatesh Rajendran I have looked up references available for ASP.NET Core https://learn.microsoft.com/en-us/azure/azure-app-configuration/quickstart-feature-flag-aspnet-core?tabs=core6x and full demo code: https://github.com/microsoft/FeatureManagement-Dotnet/tree/main/examples/FeatureFlagDemo to create a similar scenario in ASP.NET MVC application. Observed that FeatureGate attribute and feature tag helper is not available in .NET Framework MVC application. Similarly, the dependency injection is a lot simpler in ASP.NET core MVC.

Here is the thing that can get you started with MVC .NET Framework (from the scaffold code).

• Add the following code in Global.asax.cs and make sure to add necessary dependencies such as Microsoft.FeatureManagement

public class MvcApplication : System.Web.HttpApplication
    {
        public static IFeatureManager FeatureManager;

        protected void Application_Start()
        {
            AreaRegistration.RegisterAllAreas();
            FilterConfig.RegisterGlobalFilters(GlobalFilters.Filters);
            RouteConfig.RegisterRoutes(RouteTable.Routes);
            BundleConfig.RegisterBundles(BundleTable.Bundles);

            string connString = "app config connection string";

            IConfigurationRoot configuration = new ConfigurationBuilder()
            .AddAzureAppConfiguration(options =>
            {
                options.Connect(connString).UseFeatureFlags();
            }).Build();

            IServiceCollection services = new ServiceCollection();

            services.AddSingleton<IConfiguration>(configuration).AddFeatureManagement();

            using (ServiceProvider serviceProvider = services.BuildServiceProvider())
            {
                FeatureManager = serviceProvider.GetRequiredService<IFeatureManager>();
            }
        }
    }

• Create a custom Helper Feature Class with the following code snippet:

public static MvcHtmlString Feature(this HtmlHelper htmlHelper, string featureName, MvcHtmlString content)
        {
            if (MvcApplication.FeatureManager.IsEnabledAsync(featureName).Result)
            {
                return new MvcHtmlString("<li>" + content + "</li>");
            }
            else
            {
                return MvcHtmlString.Create("");
            }                
        }

• Add this helper tag @Html.Feature in _Layout.cshtml to display Beta page only when the feature is enabled.

@Html.Feature("Beta", @Html.ActionLink("Beta", "Beta", "Beta", new { area = "" }, new { @class = "nav-link" }))

Screenshot with feature enabled:

Screenshot with feature disabled:

The full source code for Feature Management is available in https://github.com/microsoft/FeatureManagement-Dotnet/tree/main/src repo and you can implement FeatureGate attribute or HTML helpers in your .NET MVC application (not readily available for .NET Framework).
Note: this code snippet is just for reference, not production code and please make sure to validate and have dependency injection implemented with best practices.

I hope this helps and let me know if any questions. I will submit the feedback to our product team for adding example/tutorial for .NET Framework MVC application.

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