public AzureAppConfigurationOptions UseFeatureFlags()

in src/Microsoft.Extensions.Configuration.AzureAppConfiguration/AzureAppConfigurationOptions.cs [271:313]
35 lines of code
7 McCabe index (conditional complexity)

        public AzureAppConfigurationOptions UseFeatureFlags(Action<FeatureFlagOptions> configure = null)
        {
            FeatureFlagOptions options = new FeatureFlagOptions();
            configure?.Invoke(options);

            if (options.RefreshInterval < RefreshConstants.MinimumFeatureFlagRefreshInterval)
            {
                throw new ArgumentOutOfRangeException(nameof(options.RefreshInterval), options.RefreshInterval.TotalMilliseconds,
                    string.Format(ErrorMessages.RefreshIntervalTooShort, RefreshConstants.MinimumFeatureFlagRefreshInterval.TotalMilliseconds));
            }

            if (options.FeatureFlagSelectors.Count() != 0 && options.Label != null)
            {
                throw new InvalidOperationException($"Please select feature flags by either the {nameof(options.Select)} method or by setting the {nameof(options.Label)} property, not both.");
            }

            if (options.FeatureFlagSelectors.Count() == 0)
            {
                // Select clause is not present
                options.FeatureFlagSelectors.Add(new KeyValueSelector
                {
                    KeyFilter = FeatureManagementConstants.FeatureFlagMarker + "*",
                    LabelFilter = string.IsNullOrWhiteSpace(options.Label) ? LabelFilter.Null : options.Label,
                    IsFeatureFlagSelector = true
                });
            }

            foreach (KeyValueSelector featureFlagSelector in options.FeatureFlagSelectors)
            {
                _selectors.AppendUnique(featureFlagSelector);

                _ffWatchers.AppendUnique(new KeyValueWatcher
                {
                    Key = featureFlagSelector.KeyFilter,
                    Label = featureFlagSelector.LabelFilter,
                    Tags = featureFlagSelector.TagFilters,
                    // If UseFeatureFlags is called multiple times for the same key and label filters, last refresh interval wins
                    RefreshInterval = options.RefreshInterval
                });
            }

            return this;
        }