public static ObservableGroup <TKey, TValue> First <TKey, TValue>(this ObservableGroupedCollection <TKey, TValue> source, TKey key) where TKey : notnull { ObservableGroup <TKey, TValue>?group = source.FirstOrDefault(key); if (group is null) {
public static ObservableGroup <TKey, TValue> First <TKey, TValue>(this ObservableGroupedCollection <TKey, TValue> source, TKey key) { ObservableGroup <TKey, TValue>?group = source.FirstOrDefault(key); if (group is null) { ThrowArgumentExceptionForKeyNotFound(); } return(group !); }
/// <summary> /// Initializes a new instance of the <see cref="ReadOnlyObservableGroup{TKey, TValue}"/> class. /// </summary> /// <param name="group">The <see cref="ObservableGroup{TKey, TValue}"/> to wrap.</param> public ReadOnlyObservableGroup(ObservableGroup <TKey, TValue> group) : base(group) { Key = group.Key; }