jellyfin/MediaBrowser.Model/Extensions/LinqExtensions.cs
Erwin de Haan ec1f5dc317 Mayor code cleanup
Add Argument*Exceptions now use proper nameof operators.

Added exception messages to quite a few Argument*Exceptions.

Fixed rethorwing to be proper syntax.

Added a ton of null checkes. (This is only a start, there are about 500 places that need proper null handling)

Added some TODOs to log certain exceptions.

Fix sln again.

Fixed all AssemblyInfo's and added proper copyright (where I could find them)

We live in *current year*.

Fixed the use of braces.

Fixed a ton of properties, and made a fair amount of functions static that should be and can be static.

Made more Methods that should be static static.

You can now use static to find bad functions!

Removed unused variable. And added one more proper XML comment.
2019-01-10 20:38:53 +01:00

86 lines
4 KiB
C#

using System;
using System.Collections.Generic;
// TODO: @bond Remove
namespace MediaBrowser.Model.Extensions
{
// MoreLINQ - Extensions to LINQ to Objects
// Copyright (c) 2008 Jonathan Skeet. All rights reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
public static class LinqExtensions
{
/// <summary>
/// Returns all distinct elements of the given source, where "distinctness"
/// is determined via a projection and the default equality comparer for the projected type.
/// </summary>
/// <remarks>
/// This operator uses deferred execution and streams the results, although
/// a set of already-seen keys is retained. If a key is seen multiple times,
/// only the first element with that key is returned.
/// </remarks>
/// <typeparam name="TSource">Type of the source sequence</typeparam>
/// <typeparam name="TKey">Type of the projected element</typeparam>
/// <param name="source">Source sequence</param>
/// <param name="keySelector">Projection for determining "distinctness"</param>
/// <returns>A sequence consisting of distinct elements from the source sequence,
/// comparing them by the specified key projection.</returns>
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector)
{
return source.DistinctBy(keySelector, null);
}
/// <summary>
/// Returns all distinct elements of the given source, where "distinctness"
/// is determined via a projection and the specified comparer for the projected type.
/// </summary>
/// <remarks>
/// This operator uses deferred execution and streams the results, although
/// a set of already-seen keys is retained. If a key is seen multiple times,
/// only the first element with that key is returned.
/// </remarks>
/// <typeparam name="TSource">Type of the source sequence</typeparam>
/// <typeparam name="TKey">Type of the projected element</typeparam>
/// <param name="source">Source sequence</param>
/// <param name="keySelector">Projection for determining "distinctness"</param>
/// <param name="comparer">The equality comparer to use to determine whether or not keys are equal.
/// If null, the default equality comparer for <c>TSource</c> is used.</param>
/// <returns>A sequence consisting of distinct elements from the source sequence,
/// comparing them by the specified key projection.</returns>
public static IEnumerable<TSource> DistinctBy<TSource, TKey>(this IEnumerable<TSource> source,
Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
if (source == null) throw new ArgumentNullException(nameof(source));
if (keySelector == null) throw new ArgumentNullException(nameof(keySelector));
return DistinctByImpl(source, keySelector, comparer);
}
private static IEnumerable<TSource> DistinctByImpl<TSource, TKey>(IEnumerable<TSource> source,
Func<TSource, TKey> keySelector, IEqualityComparer<TKey> comparer)
{
var knownKeys = new HashSet<TKey>(comparer);
foreach (var element in source)
{
if (knownKeys.Add(keySelector(element)))
{
yield return element;
}
}
}
}
}