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Add ToLookupAsync extension methods for IQueryable #13623

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Oct 24, 2018
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Add ToLookupAsync extension methods for IQueryable #13623

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176 changes: 176 additions & 0 deletions src/EFCore/EntityFrameworkQueryableExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2843,6 +2843,182 @@ public static Task<Dictionary<TKey, TElement>> ToDictionaryAsync<TSource, TKey,

#endregion

#region ToLookup

/// <summary>
/// Creates a <see cref="ILookup{TKey, TValue}" /> from an <see cref="IQueryable{T}" /> by enumerating it
/// asynchronously
/// according to a specified key selector function.
/// </summary>
/// <remarks>
/// Multiple active operations on the same context instance are not supported. Use 'await' to ensure
/// that any asynchronous operations have completed before calling another method on this context.
/// </remarks>
/// <typeparam name="TSource">
/// The type of the elements of <paramref name="source" />.
/// </typeparam>
/// <typeparam name="TKey">
/// The type of the key returned by <paramref name="keySelector" /> .
/// </typeparam>
/// <param name="source">
/// An <see cref="IQueryable{T}" /> to create a <see cref="ILookup{TKey, TValue}" /> from.
/// </param>
/// <param name="keySelector"> A function to extract a key from each element. </param>
/// <param name="cancellationToken">
/// A <see cref="CancellationToken" /> to observe while waiting for the task to complete.
/// </param>
/// <returns>
/// A task that represents the asynchronous operation.
/// The task result contains a <see cref="ILookup{TKey, TSource}" /> that contains selected keys and values.
/// </returns>
public static Task<ILookup<TKey, TSource>> ToLookupAsync<TSource, TKey>(
[NotNull] this IQueryable<TSource> source,
[NotNull] Func<TSource, TKey> keySelector,
CancellationToken cancellationToken = default)
{
Check.NotNull(source, nameof(source));
Check.NotNull(keySelector, nameof(keySelector));

return source.AsAsyncEnumerable().ToLookup(keySelector, cancellationToken);
}

/// <summary>
/// Creates a <see cref="ILookup{TKey, TValue}" /> from an <see cref="IQueryable{T}" /> by enumerating it
/// asynchronously
/// according to a specified key selector function and a comparer.
/// </summary>
/// <remarks>
/// Multiple active operations on the same context instance are not supported. Use 'await' to ensure
/// that any asynchronous operations have completed before calling another method on this context.
/// </remarks>
/// <typeparam name="TSource">
/// The type of the elements of <paramref name="source" />.
/// </typeparam>
/// <typeparam name="TKey">
/// The type of the key returned by <paramref name="keySelector" /> .
/// </typeparam>
/// <param name="source">
/// An <see cref="IQueryable{T}" /> to create a <see cref="ILookup{TKey, TValue}" /> from.
/// </param>
/// <param name="keySelector"> A function to extract a key from each element. </param>
/// <param name="comparer">
/// An <see cref="IEqualityComparer{TKey}" /> to compare keys.
/// </param>
/// <param name="cancellationToken">
/// A <see cref="CancellationToken" /> to observe while waiting for the task to complete.
/// </param>
/// <returns>
/// A task that represents the asynchronous operation.
/// The task result contains a <see cref="ILookup{TKey, TSource}" /> that contains selected keys and values.
/// </returns>
public static Task<ILookup<TKey, TSource>> ToLookupAsync<TSource, TKey>(
[NotNull] this IQueryable<TSource> source,
[NotNull] Func<TSource, TKey> keySelector,
[NotNull] IEqualityComparer<TKey> comparer,
CancellationToken cancellationToken = default)
{
Check.NotNull(source, nameof(source));
Check.NotNull(keySelector, nameof(keySelector));
Check.NotNull(comparer, nameof(comparer));

return source.AsAsyncEnumerable().ToLookup(keySelector, comparer, cancellationToken);
}

/// <summary>
/// Creates a <see cref="ILookup{TKey, TValue}" /> from an <see cref="IQueryable{T}" /> by enumerating it
/// asynchronously
/// according to a specified key selector and an element selector function.
/// </summary>
/// <remarks>
/// Multiple active operations on the same context instance are not supported. Use 'await' to ensure
/// that any asynchronous operations have completed before calling another method on this context.
/// </remarks>
/// <typeparam name="TSource">
/// The type of the elements of <paramref name="source" />.
/// </typeparam>
/// <typeparam name="TKey">
/// The type of the key returned by <paramref name="keySelector" /> .
/// </typeparam>
/// <typeparam name="TElement">
/// The type of the value returned by <paramref name="elementSelector" />.
/// </typeparam>
/// <param name="source">
/// An <see cref="IQueryable{T}" /> to create a <see cref="ILookup{TKey, TValue}" /> from.
/// </param>
/// <param name="keySelector"> A function to extract a key from each element. </param>
/// <param name="elementSelector"> A transform function to produce a result element value from each element. </param>
/// <param name="cancellationToken">
/// A <see cref="CancellationToken" /> to observe while waiting for the task to complete.
/// </param>
/// <returns>
/// A task that represents the asynchronous operation.
/// The task result contains a <see cref="ILookup{TKey, TElement}" /> that contains values of type
/// <typeparamref name="TElement" /> selected from the input sequence.
/// </returns>
public static Task<ILookup<TKey, TElement>> ToLookupAsync<TSource, TKey, TElement>(
[NotNull] this IQueryable<TSource> source,
[NotNull] Func<TSource, TKey> keySelector,
[NotNull] Func<TSource, TElement> elementSelector,
CancellationToken cancellationToken = default)
{
Check.NotNull(source, nameof(source));
Check.NotNull(keySelector, nameof(keySelector));
Check.NotNull(elementSelector, nameof(elementSelector));

return source.AsAsyncEnumerable().ToLookup(keySelector, elementSelector, cancellationToken);
}

/// <summary>
/// Creates a <see cref="ILookup{TKey, TValue}" /> from an <see cref="IQueryable{T}" /> by enumerating it
/// asynchronously
/// according to a specified key selector function, a comparer, and an element selector function.
/// </summary>
/// <remarks>
/// Multiple active operations on the same context instance are not supported. Use 'await' to ensure
/// that any asynchronous operations have completed before calling another method on this context.
/// </remarks>
/// <typeparam name="TSource">
/// The type of the elements of <paramref name="source" />.
/// </typeparam>
/// <typeparam name="TKey">
/// The type of the key returned by <paramref name="keySelector" /> .
/// </typeparam>
/// <typeparam name="TElement">
/// The type of the value returned by <paramref name="elementSelector" />.
/// </typeparam>
/// <param name="source">
/// An <see cref="IQueryable{T}" /> to create a <see cref="ILookup{TKey, TValue}" /> from.
/// </param>
/// <param name="keySelector"> A function to extract a key from each element. </param>
/// <param name="elementSelector"> A transform function to produce a result element value from each element. </param>
/// <param name="comparer">
/// An <see cref="IEqualityComparer{TKey}" /> to compare keys.
/// </param>
/// <param name="cancellationToken">
/// A <see cref="CancellationToken" /> to observe while waiting for the task to complete.
/// </param>
/// <returns>
/// A task that represents the asynchronous operation.
/// The task result contains a <see cref="ILookup{TKey, TElement}" /> that contains values of type
/// <typeparamref name="TElement" /> selected from the input sequence.
/// </returns>
public static Task<ILookup<TKey, TElement>> ToLookupAsync<TSource, TKey, TElement>(
[NotNull] this IQueryable<TSource> source,
[NotNull] Func<TSource, TKey> keySelector,
[NotNull] Func<TSource, TElement> elementSelector,
[NotNull] IEqualityComparer<TKey> comparer,
CancellationToken cancellationToken = default)
{
Check.NotNull(source, nameof(source));
Check.NotNull(keySelector, nameof(keySelector));
Check.NotNull(elementSelector, nameof(elementSelector));
Check.NotNull(comparer, nameof(comparer));

return source.AsAsyncEnumerable().ToLookup(keySelector, elementSelector, comparer, cancellationToken);
}

#endregion

#region ForEach

/// <summary>
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6 changes: 6 additions & 0 deletions test/EFCore.Tests/Extensions/QueryableExtensionsTest.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -304,6 +304,12 @@ public async Task Extension_methods_throw_on_non_async_source()
await SourceNonAsyncEnumerableTest<int>(() => Source().ToDictionaryAsync(e => e, ReferenceEqualityComparer.Instance));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToDictionaryAsync(e => e, e => e, ReferenceEqualityComparer.Instance));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToDictionaryAsync(e => e, e => e, ReferenceEqualityComparer.Instance, new CancellationToken()));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToLookupAsync(e => e));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToLookupAsync(e => e, e => e));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToLookupAsync(e => e, ReferenceEqualityComparer.Instance));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToLookupAsync(e => e, ReferenceEqualityComparer.Instance));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToLookupAsync(e => e, e => e, ReferenceEqualityComparer.Instance));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToLookupAsync(e => e, e => e, ReferenceEqualityComparer.Instance, new CancellationToken()));
await SourceNonAsyncEnumerableTest<int>(() => Source().ToListAsync());

Assert.Equal(
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