using System.Configuration.Provider; namespace System.Configuration { public class SettingsProviderCollection : ProviderCollection { public new SettingsProvider this[string name] { get { return (SettingsProvider)base[name]; } } public override void Add(ProviderBase provider) { global::<PrivateImplementationDetails>.ThrowIfNull(provider, "provider"); if (!(provider is SettingsProvider)) throw new ArgumentException(System.SR.Format(System.SR.Config_provider_must_implement_type, typeof(SettingsProvider)), "provider"); base.Add(provider); } } }