Merge pull request #267522 from zhiyuanliang-ms/zhiyuanliang/update-how-to-use-feature-filter

Azure App Configuration - Use TimeWindowFilter as example in feature filter tutorial

Author: JamesJBarnett

articles/azure-app-configuration/howto-feature-filters-aspnet-core.md

@@ -5,10 +5,10 @@ description: Learn how to use feature filters in Azure App Configuration to enab
 ms.service: azure-app-configuration
 ms.devlang: csharp
 ms.custom: devx-track-csharp
-author: maud-lv
-ms.author: malev
+author: zhiyuanliang
+ms.author: zhiyuanliang
 ms.topic: how-to
-ms.date: 01/12/2024
+ms.date: 02/28/2024
 #Customerintent: As a developer, I want to create a feature filter to activate a feature flag depending on a specific scenario.
 ---
 
@@ -18,68 +18,71 @@ Feature flags allow you to activate or deactivate functionality in your applicat
 
 In contrast, a _conditional feature flag_ allows the feature flag to be enabled or disabled dynamically. The application may behave differently, depending on the feature flag criteria. Suppose you want to show your new feature to a small subset of users at first. A conditional feature flag allows you to enable the feature flag for some users while disabling it for others. _Feature filters_ determine the state of the feature flag each time it's evaluated.
 
-The `Microsoft.FeatureManagement` library includes three feature filters:
+The `Microsoft.FeatureManagement` library includes the following built-in feature filters accessible from the Azure App Configuration portal.
 
-- `PercentageFilter` enables the feature flag based on a percentage.
-- `TimeWindowFilter` enables the feature flag during a specified window of time.
-- `TargetingFilter` enables the feature flag for specified users and groups.
+- **Time window filter** enables the feature flag during a specified window of time.
+- **Targeting filter** enables the feature flag for specified users and groups.
 
-You can also create your own feature filter that implements the Microsoft.FeatureManagement.IFeatureFilter interface.
+You can also create your own feature filter that implements the `Microsoft.FeatureManagement.IFeatureFilter` interface. For more information, see [Implementing a Feature Filter](https://github.com/microsoft/FeatureManagement-Dotnet#implementing-a-feature-filter).
 
 ## Prerequisites
 
-- An App Configuration store. [Create a store](./quickstart-azure-app-configuration-create.md#create-an-app-configuration-store).
+- Follow the instructions in [Quickstart: Add feature flags to an ASP.NET Core app](./quickstart-feature-flag-aspnet-core.md) to create a web app with a feature flag.
+- Install the [`Microsoft.FeatureManagement.AspNetCore`](https://www.nuget.org/packages/Microsoft.FeatureManagement.AspNetCore/) package of version **3.0.0** or later.
 
 ## Register a feature filter
 
-You register a feature filter by calling the `AddFeatureFilter` method, specifying the type name of the desired feature filter. For example, the following code registers `PercentageFilter`:
+If you have a [custom feature filter](https://github.com/microsoft/FeatureManagement-Dotnet#implementing-a-feature-filter), you can register it by calling the `AddFeatureFilter` method.
 
 ```csharp
-public void ConfigureServices(IServiceCollection services)
-{
-    services.AddControllersWithViews();
-    services.AddFeatureManagement().AddFeatureFilter<PercentageFilter>();
-}
+services.AddFeatureManagement()
+        .AddFeatureFilter<MyCriteriaFilter>();
 ```
 
-## Configure a feature filter in Azure App Configuration
+Starting with version *3.0.0* of `Microsoft.FeatureManagement`, the following [built-in filters](https://github.com/microsoft/FeatureManagement-Dotnet#built-in-feature-filters) are registered automatically as part of the `AddFeatureManagement` call, so you don't need to register them.
 
-Some feature filters have additional settings. For example, `PercentageFilter` activates a feature based on a percentage. It has a setting defining the percentage to use.
+- `TimeWindowFilter`
+- `ContextualTargetingFilter`
+- `PercentageFilter`
 
-You can configure these settings for feature flags defined in Azure App Configuration. For example, follow these steps to use `PercentageFilter` to enable the feature flag for 50% of requests to a web app:
+> [!TIP]
+> For more information on using `TargetingFilter`, see [Enable staged rollout of features for targeted audiences](./howto-targetingfilter-aspnet-core.md).
 
-1. Follow the instructions in [Quickstart: Add feature flags to an ASP.NET Core app](./quickstart-feature-flag-aspnet-core.md) to create a web app with a feature flag.
+## Add a feature filter to a feature flag
+
+In this section, you will learn how to add a feature filter to the **Beta** feature flag you created in the [Quickstart](./quickstart-feature-flag-aspnet-core.md). The following steps use the built-in `TimeWindowFilter` as an example.
 
 1. In the Azure portal, go to your configuration store and select **Feature manager**.
 
-    :::image type="content" source="./media/feature-filters/edit-beta-feature-flag.png" alt-text="Screenshot of the Azure portal, selecting the Edit option for the Beta feature flag, under Feature manager.":::
+    :::image type="content" source="./media/feature-filters/edit-beta-feature-flag.png" alt-text="Screenshot of the Azure portal, selecting the Edit option for the **Beta** feature flag, under Feature manager.":::
 
-1. On the line with the Beta feature flag you created in the quickstart, select the context menu and then **Edit**.
+1. On the line with the **Beta** feature flag you created in the quickstart, select the context menu and then **Edit**.
 
 1. In the **Edit feature flag** pane that opens, check the **Enable feature flag** checkbox if it isn't already enabled. Then check the **Use feature filter** checkbox and select **Create**.
 
     :::image type="content" source="./media/feature-filters/edit-a-feature-flag.png" alt-text="Screenshot of the Azure portal, filling out the form 'Edit feature flag'.":::
 
-1. The pane **Create a new filter** opens. Under **Filter type**, select **Targeting filter** to enable a new filter for specific users or a group.
+1. The pane **Create a new filter** opens. Under **Filter type**, select **Time window filter**.
+
+    :::image type="content" source="./media/feature-filters/add-time-window-filter.png" alt-text="Screenshot of the Azure portal, creating a new time window filter.":::
 
-    :::image type="content" source="./media/feature-filters/add-targeting-filter.png" alt-text="Screenshot of the Azure portal, creating a new targeting filter.":::
+1. Set the **Start date** to **Custom** and select a time a few minutes ahead of your current time. Set the **Expiry date** to **Never**
 
-1. Optionally expand the **Evaluation flow** menu to see a graph showing how the targeting filter is evaluated in the selected scenario. Leave the **Default Percentage** at 50. The options **Override by Groups** and **Override by Users** let you enable or disable the feature flag for select groups or users. These options are disabled by default.
 1. Select **Add** to save the new feature filter and return to the **Edit feature flag** screen.
 
 1. The feature filter you created is now listed in the feature flag details. Select **Apply** to save the new feature flag settings.
 
-    :::image type="content" source="./media/feature-filters/feature-flag-edit-apply-filter.png" alt-text="Screenshot of the Azure portal, applying new targeting filter.":::
+    :::image type="content" source="./media/feature-filters/feature-flag-edit-apply-filter.png" alt-text="Screenshot of the Azure portal, applying new time window filter.":::
 
 1. On the **Feature manager** page, the feature flag now has a **Feature filter(s)** value of **1**.
 
     :::image type="content" source="./media/feature-filters/updated-feature-flag.png" alt-text="Screenshot of the Azure portal, displaying updated feature flag.":::
 
 ## Feature filters in action
 
-To see the effects of this feature flag, launch the application and hit the **Refresh** button in your browser multiple times. You'll see that the *Beta* item appears on the toolbar about 50% of the time. It's hidden the rest of the time, because the `PercentageFilter` deactivates the *Beta* feature for a subset of requests. The following video shows this behavior in action.
+Relaunch the application you created in the [Quickstart](./quickstart-feature-flag-aspnet-core.md). If your current time is earlier than the start time set for the time window filter, the **Beta** menu item will not appear on the toolbar. This is because the **Beta** feature flag is disabled by the time window filter.
 
-:::image type="content" source="./media/feature-filters/feature-flags-percentagefilter.gif" alt-text="Screenshot of a web browser showing a targeting filter in action.":::
+Once the start time has passed, refresh your browser a few times. You will notice that the **Beta** menu item will now appear. This is because the **Beta** feature flag is now enabled by the time window filter.
 
 ## Next steps