Tutorial: Use dynamic configuration in a .NET Framework app

Data from App Configuration can be loaded as App Settings in a .NET Framework app. For more information, see the quickstart. However, as is designed by the .NET Framework, the App Settings can only refresh upon app restart. The App Configuration .NET provider is a .NET Standard library. It supports caching and refreshing configuration dynamically without app restart. This tutorial shows how you can implement dynamic configuration updates in a .NET Framework console app.

In this tutorial, you learn how to:

Prerequisites

• Azure subscription - create one for free
• Visual Studio
• .NET Framework 4.7.2 or later

Create an App Configuration store

1. To create a new App Configuration store, sign in to the Azure portal. In the upper-left corner of the home page, select Create a resource. In the Search the Marketplace box, enter App Configuration and select Enter.

   

2. Select App Configuration from the search results, and then select Create.

   

3. On the Create App Configuration pane, enter the following settings:

   Setting	Suggested value	Description
   Subscription	Your subscription	Select the Azure subscription that you want to use to test App Configuration. If your account has only one subscription, it's automatically selected and the Subscription list isn't displayed.
   Resource group	AppConfigTestResources	Select or create a resource group for your App Configuration store resource. This group is useful for organizing multiple resources that you might want to delete at the same time by deleting the resource group. For more information, see Use resource groups to manage your Azure resources.
   Resource name	Globally unique name	Enter a unique resource name to use for the App Configuration store resource. The name must be a string between 5 and 50 characters and contain only numbers, letters, and the - character. The name can't start or end with the - character.
   Location	Central US	Use Location to specify the geographic location in which your app configuration store is hosted. For the best performance, create the resource in the same region as other components of your application.
   Pricing tier	Free	Select the desired pricing tier. For more information, see the App Configuration pricing page.

4. Select Review + create to validate your settings.

5. Select Create. The deployment might take a few minutes.

6. After the deployment finishes, navigate to the App Configuration resource. Select Settings > Access keys. Make a note of the primary read-only key connection string. You'll use this connection string later to configure your application to communicate with the App Configuration store that you created.

7. Select Configuration explorer > + Create > Key-value to add the following key-value:

   Key	Value
   TestApp:Settings:Message	Data from Azure App Configuration

   Leave Label and Content Type empty.

Create a .NET Framework console app

1. Start Visual Studio and select Create a new project.

2. In Create a new project, filter on the Console project type and select Console App (.NET Framework) with C# from the project template list. Press Next.

3. In Configure your new project, enter a project name. Under Framework, select .NET Framework 4.7.2 or higher. Press Create.

Reload data from App Configuration

1. Right-click your project, and select Manage NuGet Packages. On the Browse tab, search and add the latest version of the following NuGet package to your project.

   Microsoft.Extensions.Configuration.AzureAppConfiguration

2. Open Program.cs and add following namespaces.

   using Microsoft.Extensions.Configuration;
   using Microsoft.Extensions.Configuration.AzureAppConfiguration;
   

3. Add two variables to store configuration-related objects.

   private static IConfiguration _configuration;
   private static IConfigurationRefresher _refresher;
   

4. Update the Main method to connect to App Configuration with the specified refresh options.

   static void Main(string[] args)
   {
       var builder = new ConfigurationBuilder();
       builder.AddAzureAppConfiguration(options =>
       {
           options.Connect(Environment.GetEnvironmentVariable("ConnectionString"))
                   // Load all keys that start with `TestApp:`.
                   .Select("TestApp:*")
                   // Configure to reload the key 'TestApp:Settings:Message' if it is modified.
                   .ConfigureRefresh(refresh =>
                   {
                       refresh.Register("TestApp:Settings:Message")
                              .SetCacheExpiration(TimeSpan.FromSeconds(10));
                   });
   
           _refresher = options.GetRefresher();
       });
   
       _configuration = builder.Build();
       PrintMessage().Wait();
   }
   

   In the ConfigureRefresh method, a key within your App Configuration store is registered for change monitoring. The Register method has an optional boolean parameter refreshAll that can be used to indicate whether all configuration values should be refreshed if the registered key changes. In this example, only the key TestApp:Settings:Message will be refreshed. The SetCacheExpiration method specifies the minimum time that must elapse before a new request is made to App Configuration to check for any configuration changes. In this example, you override the default expiration time of 30 seconds, specifying a time of 10 seconds instead for demonstration purposes.

5. Add a method called PrintMessage() that triggers a refresh of configuration data from App Configuration.

   private static async Task PrintMessage()
   {
       Console.WriteLine(_configuration["TestApp:Settings:Message"] ?? "Hello world!");
   
       // Wait for the user to press Enter
       Console.ReadLine();
   
       await _refresher.TryRefreshAsync();
       Console.WriteLine(_configuration["TestApp:Settings:Message"] ?? "Hello world!");
   }
   

   Calling the ConfigureRefresh method alone won't cause the configuration to refresh automatically. You call the TryRefreshAsync method from the interface IConfigurationRefresher to trigger a refresh. This design is to avoid phantom requests sent to App Configuration even when your application is idle. You can include the TryRefreshAsync call where you consider your application active. For example, it can be when you process an incoming message, an order, or an iteration of a complex task. It can also be in a timer if your application is active all the time. In this example, you call TryRefreshAsync when you press the Enter key. Note that, even if the call TryRefreshAsync fails for any reason, your application will continue to use the cached configuration. Another attempt will be made when the configured cache expiration time has passed and the TryRefreshAsync call is triggered by your application activity again. Calling TryRefreshAsync is a no-op before the configured cache expiration time elapses, so its performance impact is minimal, even if it's called frequently.

Build and run the app locally

1. Set an environment variable named ConnectionString to the read-only key connection string obtained during your App Configuration store creation.

   If you use the Windows command prompt, run the following command:

   setx ConnectionString "connection-string-of-your-app-configuration-store"
   

   If you use Windows PowerShell, run the following command:

   $Env:ConnectionString = "connection-string-of-your-app-configuration-store"
   

2. Restart Visual Studio to allow the change to take effect.

3. Press Ctrl + F5 to build and run the console app.

   

4. In the Azure portal, navigate to the Configuration explorer of your App Configuration store, and update the value of the following key.

   Key	Value
   TestApp:Settings:Message	Data from Azure App Configuration - Updated

5. Back in the running application, press the Enter key to trigger a refresh and print the updated value in the Command Prompt or PowerShell window.

   

   Note

   Since the cache expiration time was set to 10 seconds using the SetCacheExpiration method while specifying the configuration for the refresh operation, the value for the configuration setting will only be updated if at least 10 seconds have elapsed since the last refresh for that setting.

Clean up resources

If you do not want to continue using the resources created in this article, delete the resource group you created here to avoid charges.

1. Sign in to the Azure portal, and select Resource groups.
2. In the Filter by name box, enter the name of your resource group.
3. In the result list, select the resource group name to see an overview.
4. Select Delete resource group.
5. You're asked to confirm the deletion of the resource group. Enter the name of your resource group to confirm, and select Delete.

After a few moments, the resource group and all its resources are deleted.

Next steps

In this tutorial, you enabled your .NET Framework app to dynamically refresh configuration settings from App Configuration. To learn how to enable dynamic configuration in an ASP.NET Web Application (.NET Framework), continue to the next tutorial:

To learn how to use an Azure managed identity to streamline the access to App Configuration, continue to the next tutorial: