C# - GrowthBook Documentation

The GrowthBook C# SDK supports all modern .NET platforms including .NET 6+, .NET Framework 4.6.1+, and .NET Standard 2.0+. C# SDK Resources v1.1.3 growthbook-c-sharp NuGet C# example app Get help on Slack

Installation

Install via NuGet Package Manager:

dotnet add package growthbook-c-sharp

Or via Package Manager Console:

Install-Package growthbook-c-sharp

Quick Start

Get started with GrowthBook in just a few steps:

using GrowthBook;  
using Newtonsoft.Json.Linq;  

// 1. Create a context with user attributes  
var context = new Context  
{  
    Enabled = true,  
    Attributes = new JObject  
    {  
        ["id"] = "user-123",  
        ["country"] = "US",  
        ["plan"] = "premium"  
    }  
};  

// 2. Initialize GrowthBook  
var gb = new GrowthBook.GrowthBook(context);  

// 3. Load features from API (async)  
await gb.LoadFeaturesAsync("https://cdn.growthbook.io", "sdk_abc123");  

// 4. Evaluate features  
if (gb.IsOn("new-dashboard"))  
{  
    ShowNewDashboard();  
}  

var buttonColor = gb.GetFeatureValue("button-color", "blue");  
var maxRetries = gb.GetFeatureValue("max-retries", 3);

Loading Features from API

Basic API Integration

using System.Net.Http;  
using Newtonsoft.Json;  

public class FeaturesResult  
{  
    public HttpStatusCode Status { get; set; }  
    public IDictionary<string, Feature>? Features { get; set; }  
    public DateTimeOffset? DateUpdated { get; set; }  
}  

public async Task<GrowthBook.GrowthBook> InitializeGrowthBookAsync()  
{  
    var context = new Context  
    {  
        Enabled = true,  
        Attributes = GetUserAttributes()  
    };  

    var gb = new GrowthBook.GrowthBook(context);  

    // Load features from API  
    using var httpClient = new HttpClient();  
    var url = "https://cdn.growthbook.io/api/features/sdk_abc123";  
    var response = await httpClient.GetAsync(url);  

    if (response.IsSuccessStatusCode)  
    {  
        var content = await response.Content.ReadAsStringAsync();  
        var featuresResult = JsonConvert.DeserializeObject<FeaturesResult>(content);  

        // Update context with loaded features  
        context.Features = featuresResult.Features;  
        gb.UpdateContext(context);  
    }  

    return gb;  
}  

private JObject GetUserAttributes()  
{  
    return new JObject  
    {  
        ["id"] = User.Identity.Name,  
        ["email"] = User.Email,  
        ["country"] = User.Country,  
        ["plan"] = User.SubscriptionPlan  
    };  
}

Streaming Updates

Enable real-time feature updates with Server-Sent Events (SSE):

using System.Threading;  
using System.Threading.Tasks;  

public class GrowthBookManager : IDisposable  
{  
    private readonly GrowthBook.GrowthBook _gb;  
    private readonly Timer _refreshTimer;  
    private readonly HttpClient _httpClient;  

    public GrowthBookManager(Context context)  
    {  
        _gb = new GrowthBook.GrowthBook(context);  
        _httpClient = new HttpClient();  

        // Poll for updates every 60 seconds  
        _refreshTimer = new Timer(  
            async _ => await RefreshFeaturesAsync(),  
            null,  
            TimeSpan.Zero,  
            TimeSpan.FromSeconds(60)  
        );  
    }  

    private async Task RefreshFeaturesAsync()  
    {  
        try  
        {  
            var url = "https://cdn.growthbook.io/api/features/sdk_abc123";  
            var response = await _httpClient.GetAsync(url);  

            if (response.IsSuccessStatusCode)  
            {  
                var content = await response.Content.ReadAsStringAsync();  
                var result = JsonConvert.DeserializeObject<FeaturesResult>(content);  

                // Update features  
                var context = _gb.GetContext();  
                context.Features = result.Features;  
                _gb.UpdateContext(context);  

                Console.WriteLine($"Features updated: {result.Features.Count} features loaded");  
            }  
        }  
        catch (Exception ex)  
        {  
            Console.WriteLine($"Failed to refresh features: {ex.Message}");  
        }  
    }  

    public GrowthBook.GrowthBook GetGrowthBook() => _gb;  

    public void Dispose()  
    {  
        _refreshTimer?.Dispose();  
        _httpClient?.Dispose();  
    }  
}

User Attributes

Attributes are used for targeting and experiment assignment:

// Standard attributes  
var attributes = new JObject  
{  
    ["id"] = "user-123",  
    ["email"] = "user@example.com",  
    ["country"] = "US",  
    ["browser"] = "chrome"  
};  

// Custom business attributes  
var attributes = new JObject  
{  
    ["id"] = user.Id,  
    ["subscriptionTier"] = user.Tier,  
    ["lifetimeValue"] = user.LifetimeValue,  
    ["accountAge"] = (DateTime.Now - user.CreatedAt).Days,  
    ["isHighValueCustomer"] = user.LifetimeValue > 1000,  
    ["purchasedCategories"] = new JArray(user.Categories),  
    ["enabledFeatures"] = new JArray(user.Features)  
};  

var context = new Context  
{  
    Enabled = true,  
    Attributes = attributes  
};

Evaluating Features

Feature Result Properties

var result = gb.EvalFeature("my-feature");  

// Check if feature is enabled  
if (result.On)  
{  
    ShowNewFeature();  
}  

// Get feature value  
var value = result.Value; // JToken  
var typedValue = result.GetValue<string>(); // Typed accessor  

// Check the source  
switch (result.Source)  
{  
    case FeatureResult.SourceId.DefaultValue:  
        // Using default value  
        break;  
    case FeatureResult.SourceId.Force:  
        // Forced value  
        break;  
    case FeatureResult.SourceId.Experiment:  
        // Value from experiment  
        var experiment = result.Experiment;  
        var experimentResult = result.ExperimentResult;  
        TrackExperiment(experiment, experimentResult);  
        break;  
}

Generic Type Accessors

The SDK provides type-safe generic methods:

// Get feature values with type safety  
var isEnabled = gb.GetFeatureValue<bool>("new-feature", false);  
var buttonColor = gb.GetFeatureValue<string>("button-color", "blue");  
var maxRetries = gb.GetFeatureValue<int>("max-retries", 3);  
var timeout = gb.GetFeatureValue<double>("api-timeout", 5.0);  

// Complex types  
var config = gb.GetFeatureValue<Dictionary<string, object>>("app-config", null);  
if (config != null)  
{  
    var apiKey = config["apiKey"]?.ToString();  
    var maxConnections = Convert.ToInt32(config["maxConnections"]);  
}

Running Experiments

Inline Experiments

var experiment = new Experiment  
{  
    Key = "button-color-test",  
    Variations = new JArray { "blue", "red", "green" },  
    Weights = new List<double> { 0.5, 0.3, 0.2 }  
};  

var result = gb.Run(experiment);  

if (result.InExperiment)  
{  
    var color = result.GetValue<string>();  
    SetButtonColor(color);  

    // Track experiment view  
    TrackExperiment(experiment, result);  
}

Experiment Configuration

var experiment = new Experiment  
{  
    // Required  
    Key = "pricing-test",  
    Variations = new JArray { 9.99, 14.99, 19.99 },  

    // Optional configuration  
    Active = true,  
    Coverage = 0.8, // 80% of users  
    Weights = new List<double> { 0.5, 0.3, 0.2 },  

    // Targeting  
    Condition = JObject.Parse(@"{""country"": ""US"", ""plan"": ""premium""}"),  
    HashAttribute = "id",  

    // Sticky bucketing  
    BucketVersion = 1,  
    MinBucketVersion = 0,  
    DisableStickyBucketing = false  
};  

var result = gb.Run(experiment);

Encryption & Security

Encrypted Features

Enable encryption for sensitive feature configurations:

// Load encrypted features  
var decryptionKey = Environment.GetEnvironmentVariable("GROWTHBOOK_DECRYPTION_KEY");  

await gb.LoadFeaturesAsync(  
    apiHost: "https://cdn.growthbook.io",  
    clientKey: "sdk_abc123",  
    httpClient: new HttpClient(),  
    decryptionKey: decryptionKey  
);

Secure Attributes

Hash sensitive attributes before sending them to GrowthBook:

using System.Security.Cryptography;  
using System.Text;  

public class SecureAttributeHelper  
{  
    private readonly string _salt;  

    public SecureAttributeHelper(string salt)  
    {  
        _salt = salt;  
    }  

    public string HashAttribute(string value)  
    {  
        using var sha256 = SHA256.Create();  
        var bytes = Encoding.UTF8.GetBytes(value + _salt);  
        var hash = sha256.ComputeHash(bytes);  
        return BitConverter.ToString(hash).Replace("-", "").ToLowerInvariant();  
    }  

    public JObject BuildSecureAttributes(User user)  
    {  
        return new JObject  
        {  
            ["id"] = user.Id,  
            // Hash sensitive attributes  
            ["email"] = HashAttribute(user.Email),  
            ["phone"] = HashAttribute(user.Phone),  
            // Non-sensitive attributes remain plain  
            ["country"] = user.Country,  
            ["plan"] = user.Plan  
        };  
    }  
}  

// Usage  
var helper = new SecureAttributeHelper(  
    Environment.GetEnvironmentVariable("GROWTHBOOK_SECURE_ATTRIBUTE_SALT")  
);  

var context = new Context  
{  
    Enabled = true,  
    Attributes = helper.BuildSecureAttributes(currentUser)  
};

Security Best Practices

// Store keys securely in configuration  
public class GrowthBookConfiguration  
{  
    public string ClientKey { get; set; }  
    public string DecryptionKey { get; set; }  
    public string SecureAttributeSalt { get; set; }  
}  

// In Startup.cs or Program.cs  
services.Configure<GrowthBookConfiguration>(  
    Configuration.GetSection("GrowthBook")  
);  

// Use in services  
public class GrowthBookService  
{  
    private readonly GrowthBookConfiguration _config;  

    public GrowthBookService(IOptions<GrowthBookConfiguration> config)  
    {  
        _config = config.Value;  
    }  

    public async Task<GrowthBook.GrowthBook> CreateGrowthBookAsync()  
    {  
        var context = new Context { Enabled = true };  
        var gb = new GrowthBook.GrowthBook(context);  

        await gb.LoadFeaturesAsync(  
            "https://cdn.growthbook.io",  
            _config.ClientKey,  
            decryptionKey: _config.DecryptionKey  
        );  

        return gb;  
    }  
}

Security Recommendations:

Never hardcode encryption keys or salts in source code
Use configuration providers (appsettings.json, environment variables, Azure Key Vault)
Rotate keys regularly and coordinate updates across all environments
Use different keys for each environment (dev, staging, production)

Sticky Bucketing

Sticky bucketing ensures consistent experiment variations across sessions:

public interface IStickyBucketService  
{  
    Task<StickyBucketAssignmentDoc> GetAssignmentsAsync(string attributeName, string attributeValue);  
    Task SaveAssignmentsAsync(StickyBucketAssignmentDoc doc);  
    Task<Dictionary<string, StickyBucketAssignmentDoc>> GetAllAssignmentsAsync(Dictionary<string, string> attributes);  
}  

public class StickyBucketAssignmentDoc  
{  
    public string AttributeName { get; set; }  
    public string AttributeValue { get; set; }  
    public Dictionary<string, string> Assignments { get; set; }  
}

Implementation Example

using Microsoft.Extensions.Caching.Memory;  

public class MemoryStickyBucketService : IStickyBucketService  
{  
    private readonly IMemoryCache _cache;  
    private readonly string _prefix = "gb_sticky_";  

    public MemoryStickyBucketService(IMemoryCache cache)  
    {  
        _cache = cache;  
    }  

    public Task<StickyBucketAssignmentDoc> GetAssignmentsAsync(  
        string attributeName,  
        string attributeValue)  
    {  
        var key = $"{_prefix}{attributeName}||{attributeValue}";  
        _cache.TryGetValue(key, out StickyBucketAssignmentDoc doc);  
        return Task.FromResult(doc);  
    }  

    public Task SaveAssignmentsAsync(StickyBucketAssignmentDoc doc)  
    {  
        var key = $"{_prefix}{doc.AttributeName}||{doc.AttributeValue}";  
        _cache.Set(key, doc, TimeSpan.FromDays(30));  
        return Task.CompletedTask;  
    }  

    public Task<Dictionary<string, StickyBucketAssignmentDoc>> GetAllAssignmentsAsync(  
        Dictionary<string, string> attributes)  
    {  
        var docs = new Dictionary<string, StickyBucketAssignmentDoc>();  

        foreach (var (attrName, attrValue) in attributes)  
        {  
            var doc = GetAssignmentsAsync(attrName, attrValue).Result;  
            if (doc != null)  
            {  
                var docKey = $"{doc.AttributeName}||{doc.AttributeValue}";  
                docs[docKey] = doc;  
            }  
        }  

        return Task.FromResult(docs);  
    }  
}  

// Configure in Startup.cs  
services.AddMemoryCache();  
services.AddSingleton<IStickyBucketService, MemoryStickyBucketService>();  

// Use with GrowthBook  
var context = new Context  
{  
    Enabled = true,  
    StickyBucketService = stickyBucketService,  
    Attributes = attributes  
};

Remote Evaluation

See the Remote Evaluation overview for more information about what Remote Evaluation is, how it works, and deployment options.

Remote evaluation evaluates feature flags on a secure server:

public class RemoteEvaluationService  
{  
    private readonly HttpClient _httpClient;  
    private readonly string _apiHost;  
    private readonly string _clientKey;  

    public RemoteEvaluationService(HttpClient httpClient, string apiHost, string clientKey)  
    {  
        _httpClient = httpClient;  
        _apiHost = apiHost;  
        _clientKey = clientKey;  
    }  

    public async Task<Dictionary<string, FeatureResult>> EvaluateFeaturesAsync(JObject attributes)  
    {  
        var url = $"{_apiHost}/api/eval/{_clientKey}";  
        var payload = new  
        {  
            attributes = attributes  
        };  

        var response = await _httpClient.PostAsJsonAsync(url, payload);  
        response.EnsureSuccessStatusCode();  

        var result = await response.Content.ReadAsAsync<Dictionary<string, FeatureResult>>();  
        return result;  
    }  
}

Async API Support

The C# SDK now provides comprehensive async APIs for non-blocking operations:

Async Feature Loading

// Load features asynchronously  
await gb.LoadFeaturesAsync(apiHost, clientKey);  

// Load features with custom HTTP client  
using var httpClient = new HttpClient();  
await gb.LoadFeaturesAsync(apiHost, clientKey, httpClient);  

// Load encrypted features  
await gb.LoadFeaturesAsync(apiHost, clientKey, httpClient, decryptionKey: "key_abc123");

Async Feature Refresh

// Refresh features in the background  
await gb.RefreshFeaturesAsync();  

// Refresh with custom timeout  
using var cts = new CancellationTokenSource(TimeSpan.FromSeconds(5));  
await gb.RefreshFeaturesAsync(cts.Token);

Task-Based Patterns

All async operations return Task or Task<T> for seamless integration with async/await:

public async Task<IActionResult> Index()  
{  
    var gb = GetGrowthBookInstance();  

    // Non-blocking feature evaluation  
    var features = await Task.Run(() => new  
    {  
        NewDashboard = gb.IsOn("new-dashboard"),  
        MaxItems = gb.GetFeatureValue("max-items", 10),  
        Theme = gb.GetFeatureValue("theme", "light")  
    });  

    return View(features);  
}

Experiment Tracking

Implement tracking callbacks to send experiment data to your analytics:

public class GrowthBookWithTracking  
{  
    private readonly GrowthBook.GrowthBook _gb;  
    private readonly IAnalyticsService _analytics;  

    public GrowthBookWithTracking(Context context, IAnalyticsService analytics)  
    {  
        _gb = new GrowthBook.GrowthBook(context);  
        _analytics = analytics;  

        // Subscribe to tracking events  
        context.TrackingCallback = TrackExperiment;  
    }  

    private void TrackExperiment(Experiment experiment, ExperimentResult result)  
    {  
        if (result.InExperiment)  
        {  
            _analytics.Track("experiment_viewed", new  
            {  
                experiment_id = experiment.Key,  
                variation_id = result.VariationId,  
                variation_value = result.Value,  
                user_id = result.HashValue  
            });  
        }  
    }  

    public GrowthBook.GrowthBook GetGrowthBook() => _gb;  
}

Tracking with Experiments from Features

var featureResult = gb.EvalFeature("premium-feature");  

if (featureResult.Source == FeatureResult.SourceId.Experiment)  
{  
    var experiment = featureResult.Experiment;  
    var result = featureResult.ExperimentResult;  

    // Track to analytics  
    analytics.Track("experiment_viewed", new  
    {  
        experiment_id = experiment.Key,  
        variation_id = result.VariationId,  
        feature_id = result.FeatureId,  
        user_id = result.HashValue,  
        in_experiment = result.InExperiment,  
        hash_used = result.HashUsed  
    });  
}

Troubleshooting & Logging

Diagnostic Logging

using Microsoft.Extensions.Logging;  

public class GrowthBookLogger  
{  
    private readonly ILogger _logger;  
    private readonly GrowthBook.GrowthBook _gb;  

    public GrowthBookLogger(GrowthBook.GrowthBook gb, ILogger<GrowthBookLogger> logger)  
    {  
        _gb = gb;  
        _logger = logger;  
    }  

    public void LogContext()  
    {  
        var context = _gb.GetContext();  
        _logger.LogInformation(  
            "GrowthBook Context: Enabled={Enabled}, Features={FeatureCount}, URL={Url}",  
            context.Enabled,  
            context.Features?.Count ?? 0,  
            context.Url  
        );  
    }  

    public void LogFeatureEvaluation(string featureKey, FeatureResult result)  
    {  
        _logger.LogDebug(  
            "Feature {FeatureKey}: On={On}, Source={Source}, Value={Value}",  
            featureKey,  
            result.On,  
            result.Source,  
            result.Value  
        );  
    }  

    public void LogExperiment(Experiment experiment, ExperimentResult result)  
    {  
        _logger.LogInformation(  
            "Experiment {ExperimentKey}: InExperiment={InExperiment}, VariationId={VariationId}, Value={Value}",  
            experiment.Key,  
            result.InExperiment,  
            result.VariationId,  
            result.Value  
        );  
    }  
}

Common Issues

Features Not Loading

public async Task<bool> VerifyFeaturesLoadedAsync()  
{  
    try  
    {  
        var context = _gb.GetContext();  

        if (context.Features == null || context.Features.Count == 0)  
        {  
            _logger.LogWarning("No features loaded in GrowthBook context");  
            return false;  
        }  

        _logger.LogInformation("Features loaded: {Count}", context.Features.Count);  
        return true;  
    }  
    catch (Exception ex)  
    {  
        _logger.LogError(ex, "Error verifying features");  
        return false;  
    }  
}

Decryption Failures

public async Task<bool> TestDecryptionAsync()  
{  
    try  
    {  
        var decryptionKey = Environment.GetEnvironmentVariable("GROWTHBOOK_DECRYPTION_KEY");  

        if (string.IsNullOrEmpty(decryptionKey))  
        {  
            _logger.LogError("GROWTHBOOK_DECRYPTION_KEY not set");  
            return false;  
        }  

        await _gb.LoadFeaturesAsync(  
            "https://cdn.growthbook.io",  
            "sdk_abc123",  
            decryptionKey: decryptionKey  
        );  

        _logger.LogInformation("Successfully loaded encrypted features");  
        return true;  
    }  
    catch (Exception ex)  
    {  
        _logger.LogError(ex, "Failed to load encrypted features");  
        return false;  
    }  
}

Health Checks

using Microsoft.Extensions.Diagnostics.HealthChecks;  

public class GrowthBookHealthCheck : IHealthCheck  
{  
    private readonly GrowthBook.GrowthBook _gb;  

    public GrowthBookHealthCheck(GrowthBook.GrowthBook gb)  
    {  
        _gb = gb;  
    }  

    public Task<HealthCheckResult> CheckHealthAsync(  
        HealthCheckContext context,  
        CancellationToken cancellationToken = default)  
    {  
        try  
        {  
            var gbContext = _gb.GetContext();  

            if (!gbContext.Enabled)  
            {  
                return Task.FromResult(  
                    HealthCheckResult.Degraded("GrowthBook is disabled")  
                );  
            }  

            var featureCount = gbContext.Features?.Count ?? 0;  

            if (featureCount == 0)  
            {  
                return Task.FromResult(  
                    HealthCheckResult.Degraded("No features loaded")  
                );  
            }  

            return Task.FromResult(  
                HealthCheckResult.Healthy($"{featureCount} features loaded")  
            );  
        }  
        catch (Exception ex)  
        {  
            return Task.FromResult(  
                HealthCheckResult.Unhealthy("GrowthBook health check failed", ex)  
            );  
        }  
    }  
}  

// Register in Startup.cs  
services.AddHealthChecks()  
    .AddCheck<GrowthBookHealthCheck>("growthbook");

Integrations

ASP.NET Core

Integrate GrowthBook with ASP.NET Core for feature flags in your web application:

// Startup.cs or Program.cs  
public class Startup  
{  
    public void ConfigureServices(IServiceCollection services)  
    {  
        // Register GrowthBook as singleton  
        services.AddSingleton<GrowthBook.GrowthBook>(sp =>  
        {  
            var context = new Context  
            {  
                Enabled = true,  
                Attributes = new JObject()  
            };  

            return new GrowthBook.GrowthBook(context);  
        });  

        // Register background service for feature refresh  
        services.AddHostedService<GrowthBookRefreshService>();  

        services.AddControllersWithViews();  
    }  
}  

// Background service for periodic refresh  
public class GrowthBookRefreshService : BackgroundService  
{  
    private readonly GrowthBook.GrowthBook _gb;  
    private readonly ILogger<GrowthBookRefreshService> _logger;  

    public GrowthBookRefreshService(  
        GrowthBook.GrowthBook gb,  
        ILogger<GrowthBookRefreshService> logger)  
    {  
        _gb = gb;  
        _logger = logger;  
    }  

    protected override async Task ExecuteAsync(CancellationToken stoppingToken)  
    {  
        // Initial load  
        await RefreshFeaturesAsync();  

        while (!stoppingToken.IsCancellationRequested)  
        {  
            await Task.Delay(TimeSpan.FromSeconds(60), stoppingToken);  
            await RefreshFeaturesAsync();  
        }  
    }  

    private async Task RefreshFeaturesAsync()  
    {  
        try  
        {  
            using var httpClient = new HttpClient();  
            var url = "https://cdn.growthbook.io/api/features/sdk_abc123";  
            var response = await httpClient.GetAsync(url);  

            if (response.IsSuccessStatusCode)  
            {  
                var content = await response.Content.ReadAsStringAsync();  
                var result = JsonConvert.DeserializeObject<FeaturesResult>(content);  

                var context = _gb.GetContext();  
                context.Features = result.Features;  
                _gb.UpdateContext(context);  

                _logger.LogInformation("Features refreshed: {Count}", result.Features.Count);  
            }  
        }  
        catch (Exception ex)  
        {  
            _logger.LogError(ex, "Failed to refresh features");  
        }  
    }  
}  

// Middleware for adding user context  
public class GrowthBookMiddleware  
{  
    private readonly RequestDelegate _next;  

    public GrowthBookMiddleware(RequestDelegate next)  
    {  
        _next = next;  
    }  

    public async Task InvokeAsync(HttpContext context, GrowthBook.GrowthBook gb)  
    {  
        // Build user attributes from HTTP context  
        var attributes = new JObject  
        {  
            ["id"] = context.User.Identity?.Name,  
            ["country"] = context.Request.Headers["CF-IPCountry"].FirstOrDefault(),  
            ["userAgent"] = context.Request.Headers["User-Agent"].FirstOrDefault(),  
            ["url"] = context.Request.Path.Value  
        };  

        // Update GrowthBook context for this request  
        var gbContext = gb.GetContext();  
        gbContext.Attributes = attributes;  
        gb.UpdateContext(gbContext);  

        // Store in HttpContext for controller access  
        context.Items["GrowthBook"] = gb;  

        await _next(context);  
    }  
}  

// Use in controller  
public class HomeController : Controller  
{  
    private readonly GrowthBook.GrowthBook _gb;  

    public HomeController(GrowthBook.GrowthBook gb)  
    {  
        _gb = gb;  
    }  

    public IActionResult Index()  
    {  
        // Use feature flags  
        var showNewDashboard = _gb.IsOn("new-dashboard");  
        var maxItems = _gb.GetFeatureValue("dashboard-max-items", 10);  

        // Track experiment  
        var colorResult = _gb.EvalFeature("dashboard-theme-color");  
        if (colorResult.Source == FeatureResult.SourceId.Experiment)  
        {  
            TrackExperiment(colorResult.Experiment, colorResult.ExperimentResult);  
        }  

        return View(new DashboardViewModel  
        {  
            ShowNewDashboard = showNewDashboard,  
            MaxItems = maxItems,  
            ThemeColor = colorResult.GetValue<string>()  
        });  
    }  

    private void TrackExperiment(Experiment experiment, ExperimentResult result)  
    {  
        // Track to your analytics service  
        Analytics.Track(User.Identity.Name, "experiment_viewed", new  
        {  
            experiment_id = experiment.Key,  
            variation_id = result.VariationId  
        });  
    }  
}

Blazor Server

Use GrowthBook with Blazor Server for reactive feature flags:

// Program.cs  
builder.Services.AddSingleton<GrowthBookService>();  
builder.Services.AddScoped<UserGrowthBookService>();  

// GrowthBookService.cs  
public class GrowthBookService  
{  
    private readonly GrowthBook.GrowthBook _gb;  
    private readonly ILogger<GrowthBookService> _logger;  

    public GrowthBookService(ILogger<GrowthBookService> logger)  
    {  
        _logger = logger;  
        var context = new Context { Enabled = true };  
        _gb = new GrowthBook.GrowthBook(context);  

        // Start background refresh  
        _ = RefreshFeaturesAsync();  
    }  

    public GrowthBook.GrowthBook GetGrowthBook() => _gb;  

    public async Task RefreshFeaturesAsync()  
    {  
        try  
        {  
            using var httpClient = new HttpClient();  
            await _gb.LoadFeaturesAsync(  
                "https://cdn.growthbook.io",  
                "sdk_abc123",  
                httpClient  
            );  

            _logger.LogInformation("Features loaded");  
        }  
        catch (Exception ex)  
        {  
            _logger.LogError(ex, "Failed to load features");  
        }  
    }  

    public event EventHandler FeaturesUpdated;  

    protected virtual void OnFeaturesUpdated()  
    {  
        FeaturesUpdated?.Invoke(this, EventArgs.Empty);  
    }  
}  

// Blazor component  
@page "/dashboard"  
@inject GrowthBookService GrowthBookService  
@implements IDisposable  

<h3>Dashboard</h3>  

@if (_newDashboard)  
{  
    <NewDashboardComponent MaxItems="@_maxItems" />  
}  
else  
{  
    <LegacyDashboardComponent MaxItems="@_maxItems" />  
}  

@code {  
    private bool _newDashboard;  
    private int _maxItems;  

    protected override void OnInitialized()  
    {  
        UpdateFeatures();  
        GrowthBookService.FeaturesUpdated += OnFeaturesUpdated;  
    }  

    private void OnFeaturesUpdated(object sender, EventArgs e)  
    {  
        UpdateFeatures();  
        StateHasChanged();  
    }  

    private void UpdateFeatures()  
    {  
        var gb = GrowthBookService.GetGrowthBook();  
        _newDashboard = gb.IsOn("new-dashboard");  
        _maxItems = gb.GetFeatureValue("max-items", 20);  
    }  

    public void Dispose()  
    {  
        GrowthBookService.FeaturesUpdated -= OnFeaturesUpdated;  
    }  
}

Supported Features

FeaturesAll versions ExperimentationAll versions ≥ v1.1.3 Sticky Bucketing≥ v1.1.0 Prerequisites≥ v1.1.0 Saved Group References≥ v1.1.0 Encrypted Features≥ v1.0.0 Streaming≥ v1.0.0 v2 Hashing≥ v1.0.0 SemVer Targeting≥ v1.0.0

Client

Server

Documentation Index

​Installation

​Quick Start

​Loading Features from API

​Basic API Integration

​Streaming Updates

​User Attributes

​Evaluating Features

​Feature Result Properties

​Generic Type Accessors

​Running Experiments

​Inline Experiments

​Experiment Configuration

​Encryption & Security

​Encrypted Features

​Secure Attributes

​Security Best Practices

​Sticky Bucketing

​Implementation Example

​Remote Evaluation

​Async API Support

​Async Feature Loading

​Async Feature Refresh

​Task-Based Patterns

​Experiment Tracking

​Tracking with Experiments from Features

​Troubleshooting & Logging

​Diagnostic Logging

​Common Issues

​Features Not Loading

​Decryption Failures

​Health Checks

​Integrations

​ASP.NET Core

​Blazor Server

​Supported Features

Installation

Quick Start

Loading Features from API

Basic API Integration

Streaming Updates

User Attributes

Evaluating Features

Feature Result Properties

Generic Type Accessors

Running Experiments

Inline Experiments

Experiment Configuration

Encryption & Security

Encrypted Features

Secure Attributes

Security Best Practices

Sticky Bucketing

Implementation Example

Remote Evaluation

Async API Support

Async Feature Loading

Async Feature Refresh

Task-Based Patterns

Experiment Tracking

Tracking with Experiments from Features

Troubleshooting & Logging

Diagnostic Logging

Common Issues

Features Not Loading

Decryption Failures

Health Checks

Integrations

ASP.NET Core

Blazor Server

Supported Features