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;
}
