Update the recommended way to reference feature flag name in README (#275)

* update the recommended way to reference feature flag name

* remove nameof

* remove recommended referencing way

* using string literals directly

Author: zhiyuanliang-ms

README.md

@@ -138,20 +138,6 @@ A `RequirementType` of `All` changes the traversal. First, if there are no filte
 ```
 
 In the above example, `FeatureW` specifies a `RequirementType` of `All`, meaning all of it's filters must evaluate to true for the feature to be enabled. In this case, the feature will be enabled for 50% of users during the specified time window.
-
-### Referencing
-
-To make it easier to reference these feature flags in code, we recommend to define feature flag variables like below.
-
-``` C#
-// Define feature flags in an enum
-public enum MyFeatureFlags
-{
-    FeatureT,
-    FeatureU,
-    FeatureV
-}
-```
 
 ### Service Registration
 
@@ -187,7 +173,7 @@ The basic form of feature management is checking if a feature is enabled and the
 …
 IFeatureManager featureManager;
 …
-if (await featureManager.IsEnabledAsync(nameof(MyFeatureFlags.FeatureU)))
+if (await featureManager.IsEnabledAsync("FeatureX"))
 {
     // Do something
 }
@@ -216,7 +202,7 @@ The feature management library provides functionality in ASP.NET Core and MVC to
 MVC controller and actions can require that a given feature, or one of any list of features, be enabled in order to execute. This can be done by using a `FeatureGateAttribute`, which can be found in the `Microsoft.FeatureManagement.Mvc` namespace. 
 
 ``` C#
-[FeatureGate(MyFeatureFlags.FeatureX)]
+[FeatureGate("FeatureX")]
 public class HomeController : Controller
 {
     …
@@ -226,14 +212,14 @@ public class HomeController : Controller
 The `HomeController` above is gated by "FeatureX". "FeatureX" must be enabled before any action the `HomeController` contains can be executed. 
 
 ``` C#
-[FeatureGate(MyFeatureFlags.FeatureY)]
+[FeatureGate("FeatureX")]
 public IActionResult Index()
 {
     return View();
 }
 ```
 
-The `Index` MVC action above requires "FeatureY" to be enabled before it can execute. 
+The `Index` MVC action above requires "FeatureX" to be enabled before it can execute. 
 
 ### Disabled Action Handling
 
@@ -251,7 +237,7 @@ public interface IDisabledFeaturesHandler
 In MVC views `<feature>` tags can be used to conditionally render content based on whether a feature is enabled or not.
 
 ``` HTML+Razor
-<feature name=@nameof(MyFeatureFlags.FeatureX)>
+<feature name="FeatureX">
   <p>This can only be seen if 'FeatureX' is enabled.</p>
 </feature>
 ```
@@ -277,17 +263,17 @@ The feature management pipeline supports async MVC Action filters, which impleme
 ``` C#
 services.AddMvc(o => 
 {
-    o.Filters.AddForFeature<SomeMvcFilter>(nameof(MyFeatureFlags.FeatureV));
+    o.Filters.AddForFeature<SomeMvcFilter>("FeatureX");
 });
 ```
 
-The code above adds an MVC filter named `SomeMvcFilter`. This filter is only triggered within the MVC pipeline if the feature it specifies, "FeatureV", is enabled.
+The code above adds an MVC filter named `SomeMvcFilter`. This filter is only triggered within the MVC pipeline if the feature it specifies, "FeatureX", is enabled.
 
 ### Razor Pages
 MVC Razor pages can require that a given feature, or one of any list of features, be enabled in order to execute. This can be done by using a `FeatureGateAttribute`, which can be found in the `Microsoft.FeatureManagement.Mvc` namespace. 
 
 ``` C#
-[FeatureGate(MyFeatureFlags.FeatureU)]
+[FeatureGate("FeatureX")]
 public class IndexModel : PageModel
 {
     public void OnGet()
@@ -296,7 +282,7 @@ public class IndexModel : PageModel
 }
 ```
 
-The code above sets up a Razor page to require the "FeatureU" to be enabled. If the feature is not enabled, the page will generate an HTTP 404 (NotFound) result.
+The code above sets up a Razor page to require the "FeatureX" to be enabled. If the feature is not enabled, the page will generate an HTTP 404 (NotFound) result.
 
 When used on Razor pages, the `FeatureGateAttribute` must be placed on the page handler type. It cannot be placed on individual handler methods.
 
@@ -305,10 +291,10 @@ When used on Razor pages, the `FeatureGateAttribute` must be placed on the page
 The feature management library can be used to add application branches and middleware that execute conditionally based on feature state.
 
 ``` C#
-app.UseMiddlewareForFeature<ThirdPartyMiddleware>(nameof(MyFeatureFlags.FeatureU));
+app.UseMiddlewareForFeature<ThirdPartyMiddleware>("FeatureX");
 ```
 
-With the above call, the application adds a middleware component that only appears in the request pipeline if the feature "FeatureU" is enabled. If the feature is enabled/disabled during runtime, the middleware pipeline can be changed dynamically.
+With the above call, the application adds a middleware component that only appears in the request pipeline if the feature "FeatureX" is enabled. If the feature is enabled/disabled during runtime, the middleware pipeline can be changed dynamically.
 
 This builds off the more generic capability to branch the entire application based on a feature.