<PackageReference Include="System.Configuration.ConfigurationManager" Version="10.0.2" />

System.Configuration.SettingsPropertyCollection

Contains a collection of SettingsProperty objects.
namespace System.Configuration { public class SettingsPropertyCollection : IEnumerable, ICloneable, ICollection { public SettingsProperty this[string name] { get; } public int Count { get; } public bool IsSynchronized { get; } public object SyncRoot { get; } public SettingsPropertyCollection(); public void Add(SettingsProperty property); public void Remove(string name); public IEnumerator GetEnumerator(); public object Clone(); public void SetReadOnly(); public void Clear(); protected virtual void OnAdd(SettingsProperty property); protected virtual void OnAddComplete(SettingsProperty property); protected virtual void OnClear(); protected virtual void OnClearComplete(); protected virtual void OnRemove(SettingsProperty property); protected virtual void OnRemoveComplete(SettingsProperty property); public void CopyTo(Array array, int index); } }