.NET SDK Reference

ConfigCat .NET SDK on GitHub

Getting started

1. Install ConfigCat SDK Nuget package

Powershell / NuGet Package Manager Console

Install-Package ConfigCat.Client

.NET CLI

dotnet add package ConfigCat.Client

info

To get the ConfigCat SDK up and running in Unity, please refer to this guide.

2. Import package

using ConfigCat.Client;

3. Create the ConfigCat client with your SDK Key

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

4. Get your setting value

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

5. Dispose the ConfigCat client

You can safely dispose all clients at once or individually and release all associated resources on application exit.

ConfigCatClient.DisposeAll(); // disposes all clients
// -or-
client.Dispose(); // disposes a specific client

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.

ConfigCatClient.Get(sdkKey: "<sdkKey>") returns a client with default options.

Customizing the ConfigCat Client

To customize the SDK's behavior, you can pass an additional Action<ConfigCatClientOptions> parameter to the Get() static factory method where the ConfigCatClientOptions class is used to set up the ConfigCat Client.

IConfigCatClient client = ConfigCatClient.Get("#YOUR-SDK-KEY#", options =>
{
    options.PollingMode = PollingModes.ManualPoll;
    options.Logger = new ConsoleLogger(LogLevel.Info);
});

These are the available options on the ConfigCatClientOptions class:

Properties	Description	Default
PollingMode	Optional, sets the polling mode for the client. More about polling modes.	PollingModes.AutoPoll()
ConfigFetcher	Optional, IConfigCatConfigFetcher instance for downloading a config.	HttpClientConfigFetcher
ConfigCache	Optional, IConfigCatCache instance for caching the downloaded config.	InMemoryConfigCache
Logger	Optional, IConfigCatLogger instance for tracing.	ConsoleLogger (with WARNING level)
LogFilter	Optional, sets a custom log filter. More about log filtering.	null (none)
BaseUrl	Optional, sets the CDN base url (forward proxy, dedicated subscription) from where the SDK will download the config JSON.
HttpClientHandler	Optional, HttpClientHandler to provide network credentials and proxy settings. More about the proxy settings.	built-in HttpClientHandler
HttpTimeout	Optional, sets the underlying HTTP client's timeout. More about the HTTP timeout.	TimeSpan.FromSeconds(30)
FlagOverrides	Optional, sets the local feature flag & setting overrides. More about feature flag overrides.
DataGovernance	Optional, 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, EuOnly	Global
DefaultUser	Optional, sets the default user. More about default user.	null (none)
Offline	Optional, determines whether the client should be initialized to offline mode. More about offline mode.	false

Via the events provided by ConfigCatClientOptions you can also subscribe to the hooks (events) at the time of initialization. More about hooks.

For example:

IConfigCatClient client = ConfigCatClient.Get("#YOUR-SDK-KEY#", options =>
{
    options.ClientReady += (s, e) => Debug.WriteLine("Client is ready!");
});

info

You can acquire singleton client instances for your SDK keys using the ConfigCatClient.Get(sdkKey: "<sdkKey>") static factory method. (However, please keep in mind that subsequent calls to ConfigCatClient.Get() with the same SDK Key return a shared client instance, which was set up by the first call.)

You can close all open clients at once using the ConfigCatClient.DisposeAll() method or do it individually using the client.Dispose() method.

Anatomy of GetValueAsync()

Parameters	Description
key	REQUIRED. The key of a specific setting or feature flag. Set on ConfigCat Dashboard for each setting.
defaultValue	REQUIRED. This value will be returned in case of an error.
user	Optional, User Object. Essential when using Targeting. Read more about Targeting.

User userObject = new User("#UNIQUE-USER-IDENTIFIER#"); // Optional User Object
var value = await client.GetValueAsync("keyOfMyFeatureFlag", false, userObject);

caution

It is important to provide an argument for the defaultValue parameter, specifically for the T generic type parameter, that matches the type of the feature flag or setting you are evaluating. Please refer to the following table for the corresponding types.

Setting type mapping

Setting Kind	Type parameter T
On/Off Toggle	bool / bool?
Text	string / string?
Whole Number	int / int? / long / long?
Decimal Number	double / double?

In addition to the types mentioned above, you also have the option to provide object or object? for the type parameter regardless of the setting kind. However, this approach is not recommended as it may involve boxing.

It's important to note that providing any other type for the type parameter will result in an ArgumentException.

If you specify an allowed type but it mismatches the setting kind, an error message will be logged and defaultValue will be returned.

When relying on type inference and not explicitly specifying the type parameter, be mindful of potential type mismatch issues, especially with number types. For example, client.GetValueAsync("keyOfMyDecimalSetting", 0) will return defaultValue (0) instead of the actual value of the decimal setting because the compiler infers the type as int instead of double, that is, the call is equivalent to client.GetValueAsync<int>("keyOfMyDecimalSetting", 0), which is a type mismatch.

To correctly evaluate a decimal setting, you should use:

var value = await client.GetValueAsync("keyOfMyDecimalSetting", 0.0);
// -or-
var value = await client.GetValueAsync("keyOfMyDecimalSetting", 0d);
// -or-
var value = await client.GetValueAsync<double>("keyOfMyDecimalSetting", 0);

Anatomy of GetValueDetailsAsync()

GetValueDetailsAsync() is similar to GetValueAsync() but instead of returning the evaluated value only, it provides more detailed information about the evaluation result.

Parameters	Description
key	REQUIRED. The key of a specific setting or feature flag. Set on ConfigCat Dashboard for each setting.
defaultValue	REQUIRED. This value will be returned in case of an error.
user	Optional, User Object. Essential when using Targeting. Read more about Targeting.

User userObject = new User("#UNIQUE-USER-IDENTIFIER#"); // Optional User Object
var details = await client.GetValueDetailsAsync("keyOfMyFeatureFlag", false, userObject);

caution

It is important to provide an argument for the defaultValue parameter, specifically for the T generic type parameter, that matches the type of the feature flag or setting you are evaluating. Please refer to this table for the corresponding types.

The details result contains the following information:

Field	Type	Description
Key	string	The key of the evaluated feature flag or setting.
Value	bool / string / int / double	The evaluated value of the feature flag or setting.
User	User	The User Object used for the evaluation.
IsDefaultValue	bool	True when the default value passed to GetValueDetailsAsync() is returned due to an error.
ErrorCode	EvaluationErrorCode	In case of an error, this property contains a code that identifies the reason for the error.
ErrorMessage	string	In case of an error, this property contains the error message.
ErrorException	Exception	In case of an error, this property contains the related exception object (if any).
MatchedTargetingRule	ITargetingRule	The Targeting Rule (if any) that matched during the evaluation and was used to return the evaluated value.
MatchedPercentageOption	IPercentageOption	The Percentage Option (if any) that was used to select the evaluated value.
FetchTime	DateTime	The last download time (UTC) of the current config.

User Object

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

User userObject = new User("#UNIQUE-USER-IDENTIFIER#");

User userObject = new User("[email protected]");

Parameters	Description
Id	REQUIRED. Unique identifier of a user in your application. Can be any string value, even an email address.
Email	Optional parameter for easier Targeting Rule definitions.
Country	Optional parameter for easier Targeting Rule definitions.
Custom	Optional dictionary for custom attributes of a user for advanced Targeting Rule definitions. E.g. User role, Subscription type.

User userObject = new User("#UNIQUE-USER-IDENTIFIER#")
{
    Email = "[email protected]",
    Country = "United Kingdom",
    Custom =
    {
        ["SubscriptionType"] = "Pro",
        ["UserRole"] = "Admin"
    }
};

The Custom dictionary also allows attribute values other than string values:

User userObject = new User("#UNIQUE-USER-IDENTIFIER#")
{
    Custom =
    {
        ["Rating"] = 4.5,
        ["RegisteredAt"] = DateTimeOffset.Parse("2023-11-22 12:34:56 +00:00", CultureInfo.InvariantCulture),
        ["Roles"] = new[] { "Role1", "Role2" }
    }
};

User Object Attribute Types

All comparators support string values as User Object attribute (in some cases they need to be provided in a specific format though, see below), but some of them also support other types of values. It depends on the comparator how the values will be handled. The following rules apply:

Text-based comparators (EQUALS, IS ONE OF, etc.)

• accept string values,
• all other values are automatically converted to string (a warning will be logged but evaluation will continue as normal).

SemVer-based comparators (IS ONE OF, <, >=, etc.)

• accept string values containing a properly formatted, valid semver value,
• all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

Number-based comparators (=, <, >=, etc.)

• accept double values and all other numeric values which can safely be converted to double,
• accept string values containing a properly formatted, valid double value,
• all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

Date time-based comparators (BEFORE / AFTER)

• accept DateTime or DateTimeOffset values, which are automatically converted to a second-based Unix timestamp,
• accept double values representing a second-based Unix timestamp and all other numeric values which can safely be converted to double,
• accept string values containing a properly formatted, valid double value,
• all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

String array-based comparators (ARRAY CONTAINS ANY OF / ARRAY NOT CONTAINS ANY OF)

• accept arrays of string,
• accept string values containing a valid JSON string which can be deserialized to an array of string,
• all other values are considered invalid (a warning will be logged and the currently evaluated Targeting Rule will be skipped).

Default user

It's possible to set a default User Object that will be used on feature flag and setting evaluation. It can be useful when your application has a single user only or rarely switches users.

You can set the default User Object either on SDK initialization:

IConfigCatClient client = ConfigCatClient.Get("#YOUR-SDK-KEY#", options =>
    options.DefaultUser = new User(identifier: "[email protected]"));

...or using the SetDefaultUser() method of the ConfigCatClient object:

client.SetDefaultUser(new User(identifier: "[email protected]"));

Whenever the evaluation methods like GetValueAsync(), GetValueDetailsAsync(), etc. are called without an explicit user parameter, the SDK will automatically use the default user as a User Object.

var user = new User(identifier: "[email protected]");
client.SetDefaultUser(user);

// The default user will be used in the evaluation process.
var value = await client.GetValueAsync(key: "keyOfMyFeatureFlag", defaultValue: false);

When a user parameter is passed to the evaluation methods, it takes precedence over the default user.

var user = new User(identifier: "[email protected]");
client.SetDefaultUser(user);

var otherUser = new User(identifier: "[email protected]");

// otherUser will be used in the evaluation process.
var value = await client.GetValueAsync(key: "keyOfMyFeatureFlag", defaultValue: false, user: otherUser);

You can also remove the default user by doing the following:

client.ClearDefaultUser();

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 local cache, then all GetValueAsync() 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 = ConfigCatClient.Get("#YOUR-SDK-KEY#", options =>
{
    options.PollingMode = PollingModes.AutoPoll(pollInterval: TimeSpan.FromSeconds(95));
});

Available options:

Option Parameter	Description	Default
pollInterval	Polling interval.	60s
maxInitWaitTime	Maximum waiting time between the client initialization and the first config acquisition.	5s

Lazy loading

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

Use cacheTimeToLive parameter to manage configuration lifetime.

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

Available options:

Option Parameter	Description	Default
cacheTimeToLive	Cache 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 ForceRefreshAsync() is your application's responsibility.

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

await client.ForceRefreshAsync();

GetValueAsync() returns defaultValue if the cache is empty. Call ForceRefreshAsync() to update the cache.

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

Console.WriteLine(await client.GetValueAsync("keyOfMyTextSetting", "my default value")); // console: "my default value"
await client.ForceRefreshAsync();
Console.WriteLine(await client.GetValueAsync("keyOfMyTextSetting", "my default value")); // console: "value from server"

Hooks

The SDK provides several hooks (events), by means of which you can get notified of its actions. Via the following events you can subscribe to particular events raised by the client:

• event EventHandler<ClientReadyEventArgs> ClientReady: This event is raised when the SDK reaches the ready state. If the SDK is set up to use lazy loading or manual polling, it's considered ready right after syncing up with the config cache. If auto polling is used, the ready state is reached when the SDK has a valid config JSON loaded into memory either from cache or from HTTP. If the config couldn't be loaded neither from cache nor from HTTP, the ClientReady event fires when the auto polling's MaxInitWaitTime has passed.
• event EventHandler<ConfigFetchedEventArgs> ConfigFetched: This event is raised each time when the SDK attempts to refresh the locally cached config by fetching the latest version from the remote server. It is raised not only when ForceRefreshAsync is called but also when the refresh is initiated by the SDK automatically. Thus, this event allows you to observe potential network issues that occur under the hood.
• event EventHandler<ConfigChangedEventArgs> ConfigChanged: This event is raised first when the SDK loads a valid config JSON into memory from cache, then each time afterwards when a config JSON with changed content is downloaded via HTTP.
• event EventHandler<FlagEvaluatedEventArgs> FlagEvaluated: This event is raised each time when the SDK evaluates a feature flag or setting. The event provides the same evaluation details that you would get from GetValueDetailsAsync().
• event EventHandler<ConfigCatClientErrorEventArgs> Error: This event is raised when an error occurs within the ConfigCat SDK.

You can subscribe to these events either on initialization:

IConfigCatClient client = ConfigCatClient.Get("#YOUR-SDK-KEY#", options =>
{
    options.PollingMode = PollingModes.ManualPoll;
    options.FlagEvaluated += (s, e) => { /* handle the event */ };
});

...or directly on the ConfigCatClient instance:

client.FlagEvaluated += (s, e) => { /* handle the event */ };

Online / Offline mode

In cases where you want to prevent the SDK from making HTTP calls, you can switch it to offline mode:

client.SetOffline();

In offline mode, the SDK won't initiate HTTP requests and will work only from its cache.

To switch the SDK back to online mode, do the following:

client.SetOnline();

Using the client.IsOffline property you can check whether the SDK is in offline mode.

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 only (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 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 = ConfigCatClient.Get("localhost", options =>
{
    options.FlagOverrides = FlagOverrides.LocalFile(
        "path/to/local_flags.json", // path to the file
        true, // reload the file when it gets modified
        OverrideBehaviour.LocalOnly
    );
});

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"
  }
}

2. Complex (full-featured) structure

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

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

A convenient way to get the config JSON for a specific SDK Key is to install the ConfigCat CLI tool and execute the following command:

configcat config-json get -f v6 -p {YOUR-SDK-KEY} > config.json

(Depending on your Data Governance settings, you may need to add the --eu switch.)

Alternatively, you can download the config JSON manually, based on your Data Governance settings:

• GLOBAL: https://cdn-global.configcat.com/configuration-files/{YOUR-SDK-KEY}/config_v6.json
• EU: https://cdn-eu.configcat.com/configuration-files/{YOUR-SDK-KEY}/config_v6.json

{
  "p": {
    // hash salt, required only when confidential text comparator(s) are used
    "s": "80xCU/SlDz1lCiWFaxIBjyJeJecWjq46T4eu6GtozkM="
  },
  "s": [ // array of segments
    {
      "n": "Beta Users", // segment name
      "r": [ // array of User Conditions (there is a logical AND relation between the elements)
        {
          "a": "Email", // comparison attribute
          "c": 0, // comparator (see below)
          "l": [ // comparison value (see below)
            "[email protected]", "[email protected]"
          ]
        }
      ]
    }
  ],
  "f": { // key-value map of feature flags & settings
    "isFeatureEnabled": { // key of a particular flag / setting
      "t": 0, // setting type, possible values:
              // 0 -> on/off setting (feature flag)
              // 1 -> text setting
              // 2 -> whole number setting
              // 3 -> decimal number setting
      "r": [ // array of Targeting Rules (there is a logical OR relation between the elements)
        {
          "c": [ // array of conditions (there is a logical AND relation between the elements)
            {
              "u": { // User Condition
                "a": "Email", // comparison attribute
                "c": 2, // comparator, possible values and required comparison value types:
                        // 0  -> IS ONE OF (cleartext) + string array comparison value ("l")
                        // 1  -> IS NOT ONE OF (cleartext) + string array comparison value ("l")
                        // 2  -> CONTAINS ANY OF (cleartext) + string array comparison value ("l")
                        // 3  -> NOT CONTAINS ANY OF (cleartext) + string array comparison value ("l")
                        // 4  -> IS ONE OF (semver) + semver string array comparison value ("l")
                        // 5  -> IS NOT ONE OF (semver) + semver string array comparison value ("l")
                        // 6  -> < (semver) + semver string comparison value ("s")
                        // 7  -> <= (semver + semver string comparison value ("s")
                        // 8  -> > (semver) + semver string comparison value ("s")
                        // 9  -> >= (semver + semver string comparison value ("s")
                        // 10 -> = (number) + number comparison value ("d")
                        // 11 -> <> (number + number comparison value ("d")
                        // 12 -> < (number) + number comparison value ("d")
                        // 13 -> <= (number + number comparison value ("d")
                        // 14 -> > (number) + number comparison value ("d")
                        // 15 -> >= (number) + number comparison value ("d")
                        // 16 -> IS ONE OF (hashed) + string array comparison value ("l")
                        // 17 -> IS NOT ONE OF (hashed) + string array comparison value ("l")
                        // 18 -> BEFORE (UTC datetime) + second-based Unix timestamp number comparison value ("d")
                        // 19 -> AFTER (UTC datetime) + second-based Unix timestamp number comparison value ("d")
                        // 20 -> EQUALS (hashed) + string comparison value ("s")
                        // 21 -> NOT EQUALS (hashed) + string comparison value ("s")
                        // 22 -> STARTS WITH ANY OF (hashed) + string array comparison value ("l")
                        // 23 -> NOT STARTS WITH ANY OF (hashed) + string array comparison value ("l")
                        // 24 -> ENDS WITH ANY OF (hashed) + string array comparison value ("l")
                        // 25 -> NOT ENDS WITH ANY OF (hashed) + string array comparison value ("l")
                        // 26 -> ARRAY CONTAINS ANY OF (hashed) + string array comparison value ("l")
                        // 27 -> ARRAY NOT CONTAINS ANY OF (hashed) + string array comparison value ("l")
                        // 28 -> EQUALS (cleartext) + string comparison value ("s")
                        // 29 -> NOT EQUALS (cleartext) + string comparison value ("s")
                        // 30 -> STARTS WITH ANY OF (cleartext) + string array comparison value ("l")
                        // 31 -> NOT STARTS WITH ANY OF (cleartext) + string array comparison value ("l")
                        // 32 -> ENDS WITH ANY OF (cleartext) + string array comparison value ("l")
                        // 33 -> NOT ENDS WITH ANY OF (cleartext + string array comparison value ("l")
                        // 34 -> ARRAY CONTAINS ANY OF (cleartext) + string array comparison value ("l")
                        // 35 -> ARRAY NOT CONTAINS ANY OF (cleartext) + string array comparison value ("l")
                "l": [ // comparison value - depending on the comparator, another type of value may need
                       // to be specified (see above):
                       // "s": string
                       // "d": number
                  "@example.com"
                ]
              }
            },
            {
              "p": { // Flag Condition (Prerequisite)
                "f": "mainIntFlag", // key of prerequisite flag
                "c": 0, // comparator, possible values: 0 -> EQUALS, 1 -> NOT EQUALS
                "v": { // comparison value (value's type must match the prerequisite flag's type)
                  "i": 42
                }
              }
            },
            {
              "s": { // Segment Condition
                "s": 0, // segment index, a valid index into the top-level segment array ("s")
                "c": 1 // comparator, possible values: 0 -> IS IN SEGMENT, 1 -> IS NOT IN SEGMENT
              }
            }
          ],
          "s": { // alternatively, an array of Percentage Options ("p", see below) can also be specified
            "v": { // the value served when the rule is selected during evaluation
              "b": true
            },
            "i": "bcfb84a7"
          }
        }
      ],
      "p": [ // array of Percentage Options
        {
          "p": 10, // % value
          "v": { // the value served when the Percentage Option is selected during evaluation
            "b": true
          },
          "i": "bcfb84a7"
        },
        {
          "p": 90,
          "v": {
            "b": false
          },
          "i": "bddac6ae"
        }
      ],
      "v": { // fallback value, served when none of the Targeting Rules match,
             // no Percentage Options are defined or evaluation of these is not possible
        "b": false // depending on the setting type, another type of value may need to be specified:
                   // text setting -> "s": string
                   // whole number setting -> "i": number
                   // decimal number setting -> "d": number
      },
      "i": "430bded3" // variation id (for analytical purposes)
    }
  }
}

For a more comprehensive specification of the config JSON v6 format, you may refer to this JSON schema document.

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 = ConfigCatClient.Get("localhost", options =>
{
    options.FlagOverrides = FlagOverrides.LocalDictionary(dictionary, OverrideBehaviour.LocalOnly);
});

Logging

Setting log level

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

client.LogLevel = LogLevel.Info;

Available log levels:

Level	Description
Off	Nothing is logged.
Error	Only error level events are logged.
Warning	Default. Errors and Warnings are logged.
Info	Errors, Warnings and feature flag evaluation is logged.
Debug	All of the above plus debug info is logged.

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

ConfigCat.INFO  [5000] Evaluating 'isPOCFeatureEnabled' for User '{"Identifier":"<SOME USERID>","Email":"[email protected]","Country":"US","SubscriptionType":"Pro","Role":"Admin","version":"1.0.0"}'
  Evaluating targeting rules and applying the first match if any:
  - IF User.Email CONTAINS ANY OF ['@something.com'] THEN 'False' => no match
  - IF User.Email CONTAINS ANY OF ['@example.com'] THEN 'True' => MATCH, applying rule
  Returning 'True'.

Custom logger implementation

By default, the SDK logs to the console's standard output but it also allows you to inject any custom logger implementation via the ConfigCatClientOptions.Logger property.

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

Another sample which shows how to implement an adapter to the built-in logging framework of .NET Core/.NET 5+: See Sample Code

Log Filtering

You can define a custom log filter by providing a callback function via the ConfigCatClientOptions.LogFilter property. The callback will be called by the ConfigCat SDK each time a log event occurs (and the event passes the minimum log level specified by the IConfigCatLogger.LogLevel property). That is, the callback allows you to filter log events by level, eventId, message or exception. The formatted message string can be obtained via message.InvariantFormattedMessage. If the callback function returns true, the event will be logged, otherwise it will be skipped.

// Filter out events with id 1001 from the log.
LogFilterCallback logFilter = (LogLevel level, LogEventId eventId, ref FormattableLogMessage message, Exception? exception) => eventId != 1001;

var client = ConfigCatClient.Get("#YOUR-SDK-KEY#", options => options.LogFilter = logFilter);

caution

Please make sure that your log filter logic doesn't perform heavy computation and doesn't block the executing thread. A complex or incorrectly implemented log filter can degrade the performance of the SDK.

GetAllKeysAsync()

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

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

GetAllValuesAsync()

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

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

// invoke with User Object
User userObject = new User("#UNIQUE-USER-IDENTIFIER#");
IDictionary<string, object> settingValuesTargeting = await client.GetAllValuesAsync(userObject);

GetAllValueDetailsAsync()

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

IConfigCatClient client = ConfigCatClient.Get("#YOUR-SDK-KEY#");
IReadOnlyList<EvaluationDetails> settingValues = await client.GetAllValueDetailsAsync();

// invoke with User Object
User userObject = new User("435170f4-8a8b-4b67-a723-505ac7cdea92");
IReadOnlyList<EvaluationDetails> settingValuesTargeting = await client.GetAllValueDetailsAsync(userObject);

Snapshots and non-blocking synchronous feature flag evaluation

Currently, the ConfigCat client provides both asynchronous and synchronous methods for evaluating feature flags and settings. However, depending on the setup, the synchronous methods may block the executing thread for longer periods of time (e.g. when downloading config data from the ConfigCat CDN servers), which can lead to an unresponsive application. To prevent such issues, the problematic methods have been deprecated and are going to be removed in a future major version.

As an alternative, since v9.2.0, the .NET SDK provides a way to synchronously evaluate feature flags and settings via snapshots.

Using the Snapshot() method, you can capture the current state of the ConfigCat client (including the latest downloaded config data) and you can use the resulting snapshot object to synchronously evaluate feature flags and settings based on the captured state:

using var client = ConfigCatClient.Get("#YOUR-SDK-KEY#",
    options => options.PollingMode = PollingModes.ManualPoll);

// Make sure that the latest config data is available locally.
await client.ForceRefreshAsync();

var snapshot = client.Snapshot();

var user = new User("#UNIQUE-USER-IDENTIFIER#");
foreach (var key in snapshot.GetAllKeys())
{
    var value = snapshot.GetValue(key, default(object), user);
    Console.WriteLine($"{key}: {value}");
}

caution

Please note that when you create and utilize a snapshot, it won't refresh your local cache once the cached config data expires. Additionally, when working with shared caching, creating a snapshot also doesn't trigger a sync with the external cache, since the snapshot only captures the config instance stored in the client's memory. Therefore, it's recommended to use snapshots in conjunction with the Auto Polling mode, where the SDK automatically updates the local cache in the background. For other polling modes, you'll need to manually initiate a cache refresh by invoking ForceRefreshAsync.

In Auto Poll mode, you can use the WaitForReadyAsync method to wait for the latest config data to become available locally:

using var client = ConfigCatClient.Get("#YOUR-SDK-KEY#",
    options => options.PollingMode = PollingModes.AutoPoll());

// Make sure that the latest config data is available locally.
await client.WaitForReadyAsync();

var snapshot = client.Snapshot();

Using custom cache implementation

The ConfigCat SDK stores the downloaded config data in a local cache to minimize network traffic and enhance client performance. If you prefer to use your own cache solution, such as an external or distributed cache in your system, you can implement the IConfigCatCache interface and set the ConfigCache parameter in the setup callback of ConfigCatClient.Get. This allows you to seamlessly integrate ConfigCat with your existing caching infrastructure.

public class MyCustomCache : IConfigCatCache
{
    public string? Get(string key)
    {
        /* insert your synchronous cache read logic here */
    }

    public Task<string?> GetAsync(string key, CancellationToken cancellationToken = default)
    {
        /* insert your asynchronous cache read logic here */
    }

    public void Set(string key, string value)
    {
        /* insert your synchronous cache write logic here */
    }

    public Task SetAsync(string key, string value, CancellationToken cancellationToken = default)
    {
        /* insert your asynchronous cache write logic here */
    }
}

then

IConfigCatClient client = ConfigCatClient.Get("#YOUR-SDK-KEY#", options =>
{
    options.ConfigCache = new MyCustomCache()
});

info

The .NET SDK supports shared caching. You can read more about this feature and the required minimum SDK versions here.

Using ConfigCat behind a proxy

Provide your own network credentials (username/password) and proxy server settings (proxy server/port) by setting the HttpClientHandler property in the setup callback of ConfigCatClient.Get.

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

var myHttpClientHandler = new HttpClientHandler { Proxy = myProxySettings };

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

HTTP Timeout

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

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

The default timeout is 30 seconds.

Platform compatibility

The ConfigCat SDK supports all the widespread .NET JIT runtimes, everything that implements .NET Standard 2.0+ and supports TLS 1.2 should work. Starting with v9.3.0, it can also be used in applications that employ trimmed self-contained or various ahead-of-time (AOT) compilation deployment models.

Based on our tests, the SDK is compatible with the following runtimes/deployment models:

• .NET Framework 4.5+ (including Ngen)
• .NET Core 3.1, .NET 5+ (including Crossgen2/ReadyToRun and Native AOT)
• Mono 5.10+
• .NET for Android (formerly known as Xamarin.Android)
• .NET for iOS (formerly known as Xamarin.iOS)
• Unity 2021.3+ (Mono JIT)
• Unity 2021.3+ (IL2CPP)^*
• Universal Windows Platform 10.0.16299.0+ (.NET Native)^**
• WebAssembly (Mono AOT/Emscripten, also known as wasm-tools)

^*Unity WebGL also works but needs a bit of extra effort: you will need to enable WebGL compatibility by calling the ConfigCatClient.PlatformCompatibilityOptions.EnableUnityWebGLCompatibility method. For more details, see Sample Scripts.
^**To make the SDK work in Release builds on UWP, you will need to add <Namespace Name="System.Text.Json.Serialization.Converters" Browse="Required All"/> to your application's .rd.xml file. See also this discussion.

info

We strive to provide an extensive support for the various .NET runtimes and versions. If you still encounter an issue with the SDK on some platform, please open a GitHub issue or contact support.

Troubleshooting

When the ConfigCat SDK does not work as expected in your application, please check for the following potential problems:

• Symptom: Instead of the actual value, the default one is constantly returned by GetValueAsync() and the log contains the following message (provided that the client is set up to log error level events as described here): "Secure connection could not be established. Please make sure that your application is enabled to use TLS 1.2+."

  Problem: ConfigCat CDN servers require TLS 1.2 or newer security protocol for communication. As for allowed security protocols, please keep in mind that newer .NET runtimes rely on operating system settings, older versions, however, may need additional setup to make secure communication with the CDN servers work.

  Runtime Version	Default Protocols
  .NET Framework 4.5 and earlier	SSL 3.0, TLS 1.0
  .NET Framework 4.6	TLS 1.0, 1.1, 1.2, 1.3
  .NET Framework 4.7+, .NET Core 1.0+, .NET 5+	System (OS) Defaults

  As shown in the table above, if your application runs on .NET Framework 4.5, by default it will fail to establish a connection to the CDN servers. Read this for more details.

  Solution: The best solution to the problem is to upgrade your application to target a newer runtime but in case that is not possible, you can use the following workaround:

  ServicePointManager.SecurityProtocol |= SecurityProtocolType.Tls12;

  (Place this code at the startup of your application, before any instances of ConfigCatClient is created.)

Sample Applications

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

• Sample Console App
• Sample Multi-page Web App (ASP.NET Core MVC)
• Sample Single-page Web App (ASP.NET Core Blazor WebAssembly)
• Sample Mobile/Windows Store App (.NET MAUI)

Guides

See the following guides on how to use ConfigCat's .NET SDK:

• .NET 6
• ASP.NET Core

Look under the hood

• ConfigCat .NET SDK on GitHub
• ConfigCat .NET SDK on nuget.org