Subchapter 47.6

.NET

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.NET - Docs

This is an optional library you can install if you’re working with .NET Core. It uses an internal queue to make calls fast and non-blocking. It also batches requests and flushes asynchronously, making it perfect to use in any part of your web app or other server side application that needs performance.

.NET · Instrument Integration · PostHog/skills · Skills Docs

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
            });
    }
}

<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>

<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>

using PostHog;
var services = new ServiceCollection();
services.AddPostHog();
var serviceProvider = services.BuildServiceProvider();
var posthog = serviceProvider.GetRequiredService<IPostHogClient>();

using PostHog;
public static readonly PostHogClient PostHog = new(new PostHogOptions {
    ProjectToken = "<ph_project_token>",
    HostUrl = new Uri("https://us.i.posthog.com"),
    PersonalApiKey = Environment.GetEnvironmentVariable(
      "PostHog__PersonalApiKey")
});

var flags = await posthog.EvaluateFlagsAsync("distinct_id_of_your_user");
if (flags.IsEnabled("flag-key"))
{
    // Do something differently for this user
    // Optional: fetch the payload
    var matchedPayload = flags.GetFlagPayload("flag-key");
}

var flags = await posthog.EvaluateFlagsAsync("distinct_id_of_your_user");
var enabledVariant = flags.GetFlag("flag-key")?.VariantKey;
if (enabledVariant == "variant-key") // replace "variant-key" with the key of your variant
{
    // Do something differently for this user
    // Optional: fetch the payload
    var matchedPayload = flags.GetFlagPayload("flag-key");
}

var flags = await posthog.EvaluateFlagsAsync("distinct_id_of_your_user");
if (flags.IsEnabled("flag-key"))
{
    // Do something differently for this user
}
posthog.Capture(
    "distinct_id_of_your_user",
    "event_name",
    properties: null,
    groups: null,
    flags: flags
);

// Attach only flags accessed with IsEnabled() or GetFlag() before this call
posthog.Capture(
    "distinct_id_of_your_user",
    "event_name",
    properties: null,
    groups: null,
    flags: flags.OnlyAccessed()
);
// Attach only specific flags
posthog.Capture(
    "distinct_id_of_your_user",
    "event_name",
    properties: null,
    groups: null,
    flags: flags.Only("checkout-flow", "new-dashboard")
);

posthog.Capture(
    "distinct_id_of_your_user",
    "event_name",
    properties: new()
    {
        // Replace feature-flag-key with your flag key and "variant-key" with the key of your variant
        ["$feature/feature-flag-key"] = "variant-key",
    }
);

var flags = await posthog.EvaluateFlagsAsync(
    "distinct_id_of_your_user",
    options: new AllFeatureFlagsOptions
    {
        FlagKeysToEvaluate = new[] { "checkout-flow", "new-dashboard" },
    }
);

var flags = await posthog.EvaluateFlagsAsync(
    "distinct_id_of_the_user",
    options: new AllFeatureFlagsOptions
    {
        PersonProperties = new()
        {
            ["property_name"] = "value",
        },
        Groups = new()
        {
            new Group("your_group_type", "your_group_id")
            {
                ["group_property_name"] = "value",
            },
            new Group("another_group_type", "another_group_id")
            {
                ["group_property_name"] = "another value",
            },
        },
    }
);
if (flags.IsEnabled("flag-key"))
{
    // Do something differently for this user
}

var posthog = new PostHogClient(new PostHogOptions
{
    ProjectToken = "<ph_project_token>",
    HostUrl = new Uri("https://us.i.posthog.com"),
    EvaluationContexts = ["main-app", "api", "backend"],
});

var flags = await posthog.EvaluateFlagsAsync("user_distinct_id");
var variant = flags.GetFlag("experiment-feature-flag-key")?.VariantKey;
if (variant == "variant-name")
{
    // Do something
}

.NET

.NET - Docs

.NET

.NET - Docs

Working with .NET Feature Management

Using the core package without ASP.NET Core

Debug mode

Identifying users

Capturing events

Setting event properties

Sending page views

Error tracking

Person profiles and properties

Alias

Group analytics

Feature flags

Step 1: Evaluate flags once

Boolean feature flags

Multivariate feature flags

Step 2: Include feature flag information when capturing events

Method 1: Pass the evaluated flags snapshot to `Capture()`

Method 2: Include the `$feature/feature_flag_name` property manually

Evaluating only specific flags

Sending `$feature_flag_called` events

Advanced: Overriding server properties

Overriding GeoIP properties

Evaluation contexts

Local evaluation

Experiments (A/B tests)

GeoIP properties

Serverless environments (Azure Functions/Render/Lambda/…)

Community questions

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