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title: Feature Flags 101: A Guide for ASP.NET Core Developers
description: A practical walkthrough of implementing Feature Flags in ASP.NET Core using the Microsoft.FeatureManagement.AspNetCore NuGet package. Covers configuring flags...
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# Feature Flags 101: A Guide for ASP.NET Core Developers

**[Code4IT](https://daily.dev/sources/code4it)** · 9 min read · 0 upvotes · 0 comments

## Summary

A practical walkthrough of implementing Feature Flags in ASP.NET Core using the Microsoft.FeatureManagement.AspNetCore NuGet package. Covers configuring flags in appsettings.json, checking flags in C# code via IFeatureManager, applying the FeatureGate attribute to controllers and Razor page models, using the feature tag helper in Razor views, and setting up conditional feature filters like the percentage filter for gradual rollouts.

## Full article

daily.dev links to this article rather than hosting it. Read it at the original source: <https://www.code4it.dev/blog/feature-flags-dotnet>

## Questions this post answers

### How do I enable a feature flag only for a percentage of requests in ASP.NET Core?

Add the Microsoft.FeatureManagement.FeatureFilters.PercentageFilter to the feature management services, then define the flag in appsettings.json with an EnabledFor array containing an object with Name set to 'Percentage' and a Parameters object with a Value field, such as 60 for roughly 60% of requests enabled.

_daily.dev surfaces practical rollout techniques like this for developers rolling out ASP.NET Core features gradually._

### How do I hide a Razor Page entirely based on a feature flag in ASP.NET Core?

Apply the FeatureGate attribute to the whole PageModel class, naming the flag to watch, such as [FeatureGate("PrivacyPage")] on PrivacyModel. If the flag is enabled the page renders normally; if disabled, requests return a 404 Not Found response. Applying the attribute to individual methods like OnGet has no effect.

_Developers gating ASP.NET Core pages behind flags can track implementation patterns like this on daily.dev._

### How do I show different content depending on whether a feature flag is on or off in a Razor view?

Use the feature tag helper from Microsoft.FeatureManagement.AspNetCore after registering it in _ViewImports.cshtml with @addTagHelper *, Microsoft.FeatureManagement.AspNetCore. Wrap content in a <feature name="FlagName"> tag for the enabled case, and add a second <feature name="FlagName" negate="true"> block for the fallback content shown when the flag is off.

_daily.dev helps .NET developers keep up with Razor patterns like conditional feature rendering._

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---

Tags: [#architecture](https://daily.dev/tags/architecture), [#c#](https://daily.dev/tags/c#), [#aspnet](https://daily.dev/tags/aspnet)

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