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Getting started

1. Install ConfigCat SDK Nuget package

Install-Package ConfigCat.Client

2. Import package

using ConfigCat.Client

3. Create the ConfigCat client with your SDK Key

var client = new ConfigCatClient("#YOUR-SDK-KEY#");

4. Get your setting value

var isMyAwesomeFeatureEnabled = client.GetValue("isMyAwesomeFeatureEnabled", false);
if(isMyAwesomeFeatureEnabled)
{
doTheNewThing();
}
else
{
doTheOldThing();
}

5. Dispose ConfigCat client

You can safely Dispose() the client instance and release all associated resources on application exit.

client.Dispose();

Creating the ConfigCat Client

ConfigCat Client is responsible for:

  • managing the communication between your application and ConfigCat servers.
  • caching your setting values and feature flags.
  • serving values quickly in a failsafe way.

new ConfigCatClient() creates a client with default options.

PropertiesDescriptionDefault
SdkKeyREQUIRED. SDK Key to access your feature flags and configurations. Get it from ConfigCat Dashboard.
PollingModeOptional, sets the polling mode for the client. More about polling modes.PollingModes.AutoPoll()
ConfigCacheOptional, IConfigCache instance for cache the config.InMemoryConfigCache
LoggerOptional, ILogger instance for tracing.ConsoleLogger (with WARNING level)
HttpClientHandlerOptional, HttpClientHandler to provide network credentials and proxy settings. More about the proxy settings.built-in HttpClientHandler
HttpTimeoutOptional, sets the underlying HTTP client's timeout. More about the HTTP timeout.TimeSpan.FromSeconds(30)
FlagOverridesOptional, configures local feature flag & setting overrides. More about feature flag overrides.
DataGovernanceOptional, defaults to Global. Describes the location of your feature flag and setting data within the ConfigCat CDN. This parameter needs to be in sync with your Data Governance preferences. More about Data Governance. Available options: Global, EuOnlyGlobal
caution

We strongly recommend you to use the ConfigCatClient as a Singleton object in your application. If you want to use multiple SDK Keys in the same application, create only one ConfigCatClient per SDK Key.

Anatomy of GetValue(), GetValueAsync()

ParametersDescription
keyREQUIRED. Setting-specific key. Set on ConfigCat Dashboard for each setting.
defaultValueREQUIRED. This value will be returned in case of an error.
userOptional, User Object. Essential when using Targeting. Read more about Targeting.
User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92");
var value = client.GetValue("keyOfMySetting", false, userObject);
User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92");
var value = await client.GetValueAsync("keyOfMySetting", false, userObject);

User Object

The User Object is essential if you'd like to use ConfigCat's Targeting feature.

User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92");
User userObject = new User("[email protected]");
ParametersDescription
IdREQUIRED. Unique identifier of a user in your application. Can be any string value, even an email address.
EmailOptional parameter for easier targeting rule definitions.
CountryOptional parameter for easier targeting rule definitions.
CustomOptional dictionary for custom attributes of a user for advanced targeting rule definitions. e.g. User role, Subscription type.
User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92") {
Email = "[email protected]",
Country = "United Kingdom",
Custom = new Dictionary<string, string> {
{"SubscriptionType", "Pro"},
{"UserRole", "Admin"}}
};

Polling Modes

The ConfigCat SDK supports 3 different polling mechanisms to acquire the setting values from ConfigCat. After latest setting values are downloaded, they are stored in the internal cache then all GetValue() calls are served from there. With the following polling modes, you can customize the SDK to best fit to your application's lifecycle.
More about polling modes.

Auto polling (default)

The ConfigCat SDK downloads and stores the latest values automatically every 60 seconds.

Use the pollInterval option parameter to change the polling interval.

IConfigCatClient client = new ConfigCatClient(options => 
{
options.SdkKey = "#YOUR-SDK-KEY#";
options.PollingMode = PollingModes.AutoPoll(pollInterval: TimeSpan.FromSeconds(95));
});

Subscribing to the OnConfigurationChanged event will get you notified about changes.

IConfigCatClient client = new ConfigCatClient(options => 
{
options.SdkKey = "#YOUR-SDK-KEY#";
var autoPoll = PollingModes.AutoPoll();
autoPoll.OnConfigurationChanged += (sender, args) =>
{
Console.WriteLine("Your config has been changed!");
};
options.PollingMode = autoPoll;
});

Available options:

Option ParameterDescriptionDefault
pollIntervalPolling interval.60s
maxInitWaitTimeMaximum waiting time between the client initialization and the first config acquisition in seconds.5s

Lazy loading

When calling GetValue() or GetValueAsync() the ConfigCat SDK downloads the latest setting values if they are not present or expired in the cache. In this case the GetValue()) or GetValueAsync() will return the setting value after the cache is updated.

Use cacheTimeToLive parameter to manage configuration lifetime.

IConfigCatClient client = new ConfigCatClient(options => 
{
options.SdkKey = "#YOUR-SDK-KEY#";
options.PollingMode = PollingModes.LazyLoad(cacheTimeToLive: TimeSpan.FromSeconds(600));
});

Available options:

Option ParameterDescriptionDefault
cacheTimeToLiveCache TTL.60s

Manual polling

Manual polling gives you full control over when the config.json (with the setting values) is downloaded. ConfigCat SDK will not update them automatically. Calling ForceRefresh() is your application's responsibility.

IConfigCatClient client = new ConfigCatClient(options => 
{
options.SdkKey = "#YOUR-SDK-KEY#";
options.PollingMode = PollingModes.ManualPoll;
});

client.ForceRefresh();

GetValue() returns defaultValue if the cache is empty. Call ForceRefresh() to update the cache.

IConfigCatClient client = new ConfigCatClient(options => 
{
options.SdkKey = "#YOUR-SDK-KEY#";
options.PollingMode = PollingModes.ManualPoll;
});

Console.WriteLine(client.GetValue("key", "my default value")); // console: "my default value"
client.ForceRefresh();
Console.WriteLine(client.GetValue("key", "my default value")); // console: "value from server"

Flag Overrides

With flag overrides you can overwrite the feature flags & settings downloaded from the ConfigCat CDN with local values. Moreover, you can specify how the overrides should apply over the downloaded values. The following 3 behaviours are supported:

  • Local/Offline mode (OverrideBehaviour.LocalOnly): When evaluating values, the SDK will not use feature flags & settings from the ConfigCat CDN, but it will use all feature flags & settings that are loaded from local-override sources.

  • Local over remote (OverrideBehaviour.LocalOverRemote): When evaluating values, the SDK will use all feature flags & settings that are downloaded from the ConfigCat CDN, plus all feature flags & settings that are loaded from local-override sources. If a feature flag or a setting is defined both in the downloaded and the local-override source then the local-override version will take precedence.

  • Remote over local (OverrideBehaviour.RemoteOverLocal): When evaluating values, the SDK will use all feature flags & settings that are downloaded from the ConfigCat CDN, plus all feature flags & settings that are loaded from local-override sources. If a feature flag or a setting is defined both in the downloaded and the local-override source then the downloaded version will take precedence.

You can load your feature flag & setting overrides from a file or from a simple Dictionary<string, object> structure.

JSON File

The SDK can be configured to load your feature flag & setting overrides from a file. You can also specify whether the file should be reloaded when it gets modified.

File

IConfigCatClient client = new ConfigCatClient(options =>
{
options.SdkKey = "localhost";
options.FlagOverrides = FlagOverrides.LocalFile(
"path/to/local_flags.json", // path to the file
true, // reload the file when it gets modified
OverrideBehaviour.LocalOnly // local/offline mode
);
});

JSON File Structure

The SDK supports 2 types of JSON structures to describe feature flags & settings.

1. Simple (key-value) structure
{
"flags": {
"enabledFeature": true,
"disabledFeature": false,
"intSetting": 5,
"doubleSetting": 3.14,
"stringSetting": "test"
}
}

This is the same format that the SDK downloads from the ConfigCat CDN. It allows the usage of all features you can do on the ConfigCat Dashboard.

You can download your current config.json from ConfigCat's CDN and use it as a baseline.

The URL to your current config.json is based on your Data Governance settings:

  • GLOBAL: https://cdn-global.configcat.com/configuration-files/{YOUR-SDK-KEY}/config_v5.json
  • EU: https://cdn-eu.configcat.com/configuration-files/{YOUR-SDK-KEY}/config_v5.json
{
"f": { // list of feature flags & settings
"isFeatureEnabled": { // key of a particular flag
"v": false, // default value, served when no rules are defined
"i": "430bded3", // variation id (for analytical purposes)
"t": 0, // feature flag's type, possible values:
// 0 -> BOOLEAN
// 1 -> STRING
// 2 -> INT
// 3 -> DOUBLE
"p": [ // list of percentage rules
{
"o": 0, // rule's order
"v": true, // value served when the rule is selected during evaluation
"p": 10, // % value
"i": "bcfb84a7" // variation id (for analytical purposes)
},
{
"o": 1, // rule's order
"v": false, // value served when the rule is selected during evaluation
"p": 90, // % value
"i": "bddac6ae" // variation id (for analytical purposes)
}
],
"r": [ // list of targeting rules
{
"o": 0, // rule's order
"a": "Identifier", // comparison attribute
"t": 2, // comparator, possible values:
// 0 -> 'IS ONE OF',
// 1 -> 'IS NOT ONE OF',
// 2 -> 'CONTAINS',
// 3 -> 'DOES NOT CONTAIN',
// 4 -> 'IS ONE OF (SemVer)',
// 5 -> 'IS NOT ONE OF (SemVer)',
// 6 -> '< (SemVer)',
// 7 -> '<= (SemVer)',
// 8 -> '> (SemVer)',
// 9 -> '>= (SemVer)',
// 10 -> '= (Number)',
// 11 -> '<> (Number)',
// 12 -> '< (Number)',
// 13 -> '<= (Number)',
// 14 -> '> (Number)',
// 15 -> '>= (Number)',
// 16 -> 'IS ONE OF (Hashed)',
// 17 -> 'IS NOT ONE OF (Hashed)'
"c": "@example.com", // comparison value
"v": true, // value served when the rule is selected during evaluation
"i": "bcfb84a7" // variation id (for analytical purposes)
}
]
},
}
}

Dictionary

You can set up the SDK to load your feature flag & setting overrides from a Dictionary<string, object>.

var dictionary = new Dictionary<string, object>
{
{"enabledFeature", true},
{"disabledFeature", false},
{"intSetting", 5},
{"doubleSetting", 3.14},
{"stringSetting", "test"},
};

IConfigCatClient client = new ConfigCatClient(options =>
{
options.SdkKey = "localhost";
options.FlagOverrides = FlagOverrides.LocalDictionary(dictionary, OverrideBehaviour.LocalOnly);
});

Logging

Setting log level

IConfigCatClient client = new ConfigCatClient("#YOUR-SDK-KEY#");

client.LogLevel = LogLevel.Info;

Available log levels:

LevelDescription
OffNothing is logged.
ErrorOnly error level events are logged.
WarningDefault. Errors and Warnings are logged.
InfoErrors, Warnings and feature flag evaluation is logged.
DebugAll of the above plus debug info is logged.

Info level logging helps to inspect the feature flag evaluation process:

ConfigCat - Info -  Evaluate 'isPOCFeatureEnabled'
User object: {"Identifier":"<SOME USERID>","Email":"[email protected]","Country":"US","Custom":{"SubscriptionType":"Pro","Role":"Admin","version":"1.0.0"}}
evaluate rule: '[email protected]' CONTAINS '@something.com' => no match
evaluate rule: '[email protected]' CONTAINS '@example.com' => match
Returning: True

Sample code on how to create a basic file logger implementation for ConfigCat client: See Sample Code

GetAllKeys(), GetAllKeysAsync()

You can get all the setting keys from your configuration by calling the GetAllKeys() or GetAllKeysAsync() method of the ConfigCatClient.

IConfigCatClient client = new ConfigCatClient("#YOUR-SDK-KEY#");
IEnumerable<string> keys = client.GetAllKeys();
IConfigCatClient client = new ConfigCatClient("#YOUR-SDK-KEY#");
IEnumerable<string> keys = await client.GetAllKeysAsync();

GetAllValues(), GetAllValuesAsync()

Evaluates and returns the values of all feature flags and settings. Passing a User Object is optional.

IConfigCatClient client = new ConfigCatClient("#YOUR-SDK-KEY#");
IDictionary<string, object> settingValues = client.GetAllValues();

// invoke with user object
User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92");
IDictionary<string, object> settingValuesTargeting = client.GetAllValues(userObject);
IConfigCatClient client = new ConfigCatClient("#YOUR-SDK-KEY#");
IDictionary<string, object> settingValues = await client.GetAllValuesAsync();

// invoke with user object
User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92");
IDictionary<string, object> settingValuesTargeting = await client.GetAllValuesAsync(userObject);

Using ConfigCat behind a proxy

Provide your own network credentials (username/password), and proxy server settings (proxy server/port) by injecting a HttpClientHandler instance into the ConfigCatClient's configuration.

var myProxySettings = new WebProxy(proxyHost, proxyPort)
{
UseDefaultCredentials = false,
Credentials = new NetworkCredential(proxyUserName, proxyPassword)
};

var myHttpClientHandler = new HttpClientHandler { Proxy = myProxySettings };

IConfigCatClient client = new ConfigCatClient(options =>
{
options.SdkKey = "#YOUR-SDK-KEY#";
options.HttpClientHandler = myHttpClientHandler;
});

HTTP Timeout

You can set the maximum wait time for a ConfigCat HTTP response.

IConfigCatClient client = new ConfigCatClient(options =>
{
options.SdkKey = "#YOUR-SDK-KEY#";
options.HttpTimeout = TimeSpan.FromSeconds(10);
});

The default timeout is 30 seconds.

Sample Applications

Check out our Sample Applications how they use the ConfigCat SDK:

Look under the hood