Setting the file. One moment.
Chapter 184 · Feature Flags .NET
Subchapter 184.3
references/dotnet.mdMarkdown7 KBView on GitHub
The PostHog package supports any .NET platform that targets .NET Standard 2.1 or .NET 8+, including MAUI, Blazor, and console applications. The PostHog.AspNetCore package provides additional conveniences for ASP.NET Core applications such as streamlined registration, request-scoped caching, and integration with .
Note: We actively test with ASP.NET Core. Other platforms should work but haven’t been specifically tested. If you encounter issues, please report them on GitHub (opens in a new tab).
Not supported: Classic UWP (requires .NET Standard 2.0 only). Microsoft has deprecated UWP (opens in a new tab) in favor of the Windows App SDK. For Unity projects, see our dedicated Unity SDK (opens in a new tab) (currently in beta).
Terminal
PostHog AI
dotnet add package PostHog.AspNetCoreIn your Program.cs (or Startup.cs for ASP.NET Core 2.x) file, add the following code:
C#
PostHog AI
using PostHog;
var builder = WebApplication.CreateBuilder(args);
// Add PostHog to the dependency injection container as a singleton.
builder.AddPostHog();Make sure to configure PostHog with your project token, instance address, and optional personal API key. For example, in appsettings.json:
JSON
PostHog AI
{
"PostHog": {
"ProjectApiKey": "<ph_project_token>",
"HostUrl": "https://us.i.posthog.com"
}
}Note: If the host is not specified, the default host
https://us.i.posthog.comis used.
Use a secrets manager to store your personal API key. For example, when developing locally you can use the UserSecrets feature of the dotnet CLI:
Terminal
PostHog AI
dotnet user-secrets init
dotnet user-secrets set "PostHog:PersonalApiKey" "phx_..."You can find your project token and instance address in the project settings (opens in a new tab) page in PostHog.
PostHog.AspNetCore supports .NET Feature Management (opens in a new tab). This enables you to use the <feature /> tag helper and the FeatureGateAttribute in your ASP.NET Core applications to gate access to certain features using PostHog feature flags.
To use feature flags with the .NET Feature Management library, you’ll need to implement the IPostHogFeatureFlagContextProvider interface. The quickest way to do that is to inherit from the PostHogFeatureFlagContextProvider class and override the GetDistinctId and GetFeatureFlagOptionsAsync methods.
C#
PostHog AI
public class MyFeatureFlagContextProvider(IHttpContextAccessor httpContextAccessor)
: PostHogFeatureFlagContextProvider
{
protected override string? GetDistinctId()
=> httpContextAccessor.HttpContext?.User.Identity?.Name;
protected override ValueTask<FeatureFlagOptions> GetFeatureFlagOptionsAsync()
{
// In a real app, you might get this information from a
// database or other source for the current user.
return ValueTask.FromResult(
new FeatureFlagOptions
{
PersonProperties = new Dictionary<string, object?>
{
["email"] = "some-test@example.com"
},
OnlyEvaluateLocally = true
});
}
}Then, register your implementation in Program.cs (or Startup.cs):
C#
PostHog AI
var builder = WebApplication.CreateBuilder(args);
builder.AddPostHog(options => {
options.UseFeatureManagement<MyFeatureFlagContextProvider>();
});With this in place, you can now use feature tag helpers in your Razor views:
HTML
PostHog AI
<feature name="awesome-new-feature">
<p>This is the new feature!</p>
</feature>
<feature name="awesome-new-feature" negate="true">
<p>Sorry, no awesome new feature for you.</p>
</feature>Multivariate feature flags are also supported:
HTML
PostHog AI
<feature name="awesome-new-feature" value="variant-a">
<p>This is the new feature variant A!</p>
</feature>
<feature name="awesome-new-feature" value="variant-b">
<p>This is the new feature variant B!</p>
</feature>You can also use the FeatureGateAttribute to gate access to controllers or actions:
C#
PostHog AI
[FeatureGate("awesome-new-feature")]
public class NewFeatureController : Controller
{
public IActionResult Index()
{
return View();
}
}If you’re not using ASP.NET Core (for example, in a console application, MAUI app, or Blazor WebAssembly), install the PostHog package instead of PostHog.AspNetCore. This package has no ASP.NET Core dependencies and can be used in any .NET project targeting .NET Standard 2.1 or .NET 8+.
Terminal
PostHog AI
dotnet add package PostHogThe PostHogClient class must be implemented as a singleton in your project. For PostHog.AspNetCore, this is handled by the builder.AddPostHog(); method. For the PostHog package, you can do the following if you’re using dependency injection:
C#
PostHog AI
builder.Services.AddPostHog();If you’re not using a builder (such as in a console application), you can do the following:
C#
PostHog AI
using PostHog;
var services = new ServiceCollection();
services.AddPostHog();
var serviceProvider = services.BuildServiceProvider();
var posthog = serviceProvider.GetRequiredService<IPostHogClient>();The AddPostHog methods accept an optional Action<PostHogOptions> parameter that you can use to configure the client.
If you’re not using dependency injection, you can create a static instance of the PostHogClient class and use that everywhere in your project:
C#
PostHog AI
using PostHog;
public static readonly PostHogClient PostHog = new(new PostHogOptions {
ProjectApiKey = "<ph_project_token>",
HostUrl = new Uri("https://us.i.posthog.com"),
PersonalApiKey = Environment.GetEnvironmentVariable(
"PostHog__PersonalApiKey")
});If you’re not seeing the expected events being captured, the feature flags being evaluated, or the surveys being shown, you can enable debug mode to see what’s happening.
To see detailed logging, set the log level to Debug or Trace in appsettings.json:
JSON
PostHog AI
{
"DetailedErrors": true,
"Logging": {
"LogLevel": {
"Default": "Information",
"Microsoft.AspNetCore": "Warning",
"PostHog": "Trace"
}
},
...
}Ask a question
HelpfulCould be better