Add Feature flags

Author: andrewlock

CustomFeatureFilter/CustomFeatureFilter/ClaimsFeatureFilter.cs

@@ -0,0 +1,30 @@
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.Configuration;
+using Microsoft.FeatureManagement;
+using System;
+using System.Linq;
+
+namespace CustomFeatureFilter
+{
+    [FilterAlias("Claims")]
+    public class ClaimsFeatureFilter : IFeatureFilter
+    {
+        private readonly IHttpContextAccessor _httpContextAccesor;
+
+        public ClaimsFeatureFilter(IHttpContextAccessor httpContextAccesor)
+        {
+            _httpContextAccesor = httpContextAccesor ?? throw new ArgumentNullException(nameof(httpContextAccesor));
+        }
+
+        public bool Evaluate(FeatureFilterEvaluationContext context)
+        {
+            var settings = context.Parameters.Get<ClaimsFilterSettings>();
+
+            var user = _httpContextAccesor.HttpContext.User;
+
+            return settings.RequiredClaims
+                .All(claimType => user.HasClaim(claim => claim.Type == claimType));
+        }
+    }
+        
+}

CustomFeatureFilter/CustomFeatureFilter/ClaimsFilterSettings.cs

@@ -0,0 +1,8 @@
+namespace CustomFeatureFilter
+{
+    public class ClaimsFilterSettings
+    {
+        public string[] RequiredClaims { get; set; }
+    }
+        
+}

CustomFeatureFilter/CustomFeatureFilter/CustomFeatureFilter.csproj

@@ -9,6 +9,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.AspNetCore.App" />
+    <PackageReference Include="Microsoft.FeatureManagement.AspNetCore" Version="1.0.0-preview-008560001-910" />
     <PackageReference Include="Microsoft.AspNetCore.Razor.Design" Version="2.2.0" PrivateAssets="All" />
   </ItemGroup>
 

CustomFeatureFilter/CustomFeatureFilter/FeatureFlags.cs

@@ -0,0 +1,8 @@
+namespace CustomFeatureFilter
+{
+    public static class FeatureFlags
+    {
+        public const string Beta = "Beta";
+        public const string NewWelcomeBanner = "NewWelcomeBanner";
+    }
+}

CustomFeatureFilter/CustomFeatureFilter/Pages/Index.cshtml

@@ -4,7 +4,13 @@
     ViewData["Title"] = "Home page";
 }
 
+<feature name="@FeatureFlags.Beta">
+    <div class="alert alert-primary" role="alert">
+        Congratulations - You're in the Beta test!
+    </div>
+</feature>
+
 <div class="text-center">
-    <h1 class="display-4">Welcome</h1>
+    <h1 class="display-4">@Model.WelcomeMessage</h1>
     <p>Learn about <a href="https://docs.microsoft.com/aspnet/core">building Web apps with ASP.NET Core</a>.</p>
 </div>

CustomFeatureFilter/CustomFeatureFilter/Pages/Index.cshtml.cs

@@ -4,14 +4,26 @@
 using System.Threading.Tasks;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Mvc.RazorPages;
+using Microsoft.FeatureManagement;
 
 namespace CustomFeatureFilter.Pages
 {
     public class IndexModel : PageModel
     {
-        public void OnGet()
+        private readonly IFeatureManagerSnapshot _featureManager;
+
+        public IndexModel(IFeatureManagerSnapshot featureManager)
         {
+            _featureManager = featureManager;
+        }
 
+        public string WelcomeMessage { get; set; }
+
+        public void OnGet()
+        {
+            WelcomeMessage = _featureManager.IsEnabled(FeatureFlags.NewWelcomeBanner)
+                ? "Welcome to the Beta"
+                : "Welcome";
         }
     }
 }

CustomFeatureFilter/CustomFeatureFilter/Pages/_ViewImports.cshtml

@@ -3,3 +3,4 @@
 @using CustomFeatureFilter.Data
 @namespace CustomFeatureFilter.Pages
 @addTagHelper *, Microsoft.AspNetCore.Mvc.TagHelpers
+@addTagHelper *, Microsoft.FeatureManagement.AspNetCore

CustomFeatureFilter/CustomFeatureFilter/Startup.cs

@@ -13,6 +13,7 @@
 using CustomFeatureFilter.Data;
 using Microsoft.Extensions.Configuration;
 using Microsoft.Extensions.DependencyInjection;
+using Microsoft.FeatureManagement;
 
 namespace CustomFeatureFilter
 {
@@ -45,6 +46,8 @@ public void ConfigureServices(IServiceCollection services)
 
             services.AddMvc().SetCompatibilityVersion(CompatibilityVersion.Version_2_2);
 
+            services.AddFeatureManagement()
+                    .AddFeatureFilter<ClaimsFeatureFilter>();
         }
 
         // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.

CustomFeatureFilter/CustomFeatureFilter/appsettings.json

@@ -7,5 +7,18 @@
       "Default": "Warning"
     }
   },
-  "AllowedHosts": "*"
+  "AllowedHosts": "*",
+  "FeatureManagement": {
+    "NewWelcomeBanner": true,
+    "Beta": {
+      "EnabledFor": [
+        {
+          "Name": "Claims",
+          "Parameters": {
+            "RequiredClaims": [ "Internal" ]
+          }
+        }
+      ]
+    }
+  }
 }