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));
        }
示例#2
0
 /// <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));
示例#6
0
 /// <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));