public static ObservableGroup <TKey, TValue>?FirstOrDefault <TKey, TValue>(this ObservableGroupedCollection <TKey, TValue> source, TKey key)
{
if (source.TryGetList(out var list))
{
foreach (var group in list !)
{
if (EqualityComparer <TKey> .Default.Equals(group.Key, key))
{
return(group);
}
}
return(null);
}
return(FirstOrDefaultWithLinq(source, key));
}
/// <summary>
/// Initializes a new instance of the <see cref="ReadOnlyObservableGroupedCollection{TKey, TValue}"/> class.
/// </summary>
/// <param name="collection">The source collection to wrap.</param>
public ReadOnlyObservableGroupedCollection(ObservableGroupedCollection <TKey, TValue> collection)
: this(collection.Select(static g => new ReadOnlyObservableGroup <TKey, TValue>(g)))
/// <summary>
/// Initializes a new instance of the <see cref="ReadOnlyObservableGroupedCollection{TKey, TValue}"/> class.
/// </summary>
/// <param name="collection">The source collection to wrap.</param>
public ReadOnlyObservableGroupedCollection(ObservableGroupedCollection <TKey, TValue> collection)
: this(collection.Select(g => new ReadOnlyObservableGroup <TKey, TValue>(g)))
{
((INotifyCollectionChanged)collection).CollectionChanged += this.OnSourceCollectionChanged;
}
public static TValue ElementAt <TKey, TValue>(
this ObservableGroupedCollection <TKey, TValue> source,
TKey key,
int index)
=> source.First(key)[index];
private static ObservableGroup <TKey, TValue>?FirstOrDefaultWithLinq <TKey, TValue>(
ObservableGroupedCollection <TKey, TValue> source,
TKey key)
=> source.FirstOrDefault(group => EqualityComparer <TKey> .Default.Equals(group.Key, key));
/// <summary>
/// Return the first group with <paramref name="key"/> key or null if not found.
/// </summary>
/// <typeparam name="TKey">The type of the group key.</typeparam>
/// <typeparam name="TValue">The type of the items in the collection.</typeparam>
/// <param name="source">The source <see cref="ObservableGroupedCollection{TKey, TValue}"/> instance.</param>
/// <param name="key">The key of the group to query.</param>
/// <returns>The first group matching <paramref name="key"/> or null.</returns>
public static ObservableGroup <TKey, TValue> FirstOrDefault <TKey, TValue>(this ObservableGroupedCollection <TKey, TValue> source, TKey key)
=> source.FirstOrDefault(group => GroupKeyPredicate(group, key));