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Merged
kevinwell merged 2 commits into from
Mar 11, 2026
Merged

Add AsReadOnlyCollection #176

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31cff16
Add AsReadOnlyCollection
MrSmoke Mar 11, 2026
36600cb
Use ToArray over ToList when enumerating
MrSmoke Mar 11, 2026
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75 changes: 48 additions & 27 deletions src/Primitives/Primitives/src/Extensions/EnumerableExtensions.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -3,7 +3,6 @@
using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Diagnostics.CodeAnalysis;
using System.Linq;

Expand All @@ -15,7 +14,7 @@ public static partial class EnumerableExtensions
/// <param name="source"></param>
/// <param name="value">The first element if found</param>
/// <typeparam name="T"></typeparam>
/// <returns>True if element contains an item, otherwise false</returns>
/// <returns>True if <paramref name="source"/> contains an item, otherwise false</returns>
/// <exception cref="ArgumentNullException"></exception>
public static bool TryGetFirstValue<T>(this IEnumerable<T> source, [MaybeNullWhen(false)] out T value)
{
Expand All @@ -30,11 +29,11 @@ public static bool TryGetFirstValue<T>(this IEnumerable<T> source, [MaybeNullWhe
return false;
}
#else
if (source is ICollection<T> {Count: 0} or ICollection {Count: 0})
{
value = default;
return false;
}
if (source is ICollection<T> {Count: 0} or ICollection {Count: 0})
{
value = default;
return false;
}
#endif

if (source is IList<T> list)
Expand All @@ -59,44 +58,67 @@ public static bool TryGetFirstValue<T>(this IEnumerable<T> source, [MaybeNullWhe
/// <summary>
/// Casts a sequence to an <see cref="ICollection{T}"/>, otherwise enumerates the sequence.
/// </summary>
/// <param name="enumerable"></param>
/// <param name="source"></param>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static ICollection<T> AsCollection<T>(this IEnumerable<T> enumerable)
public static ICollection<T> AsCollection<T>(this IEnumerable<T> source)
{
if (enumerable is ICollection<T> collection)
if (source is null)
throw new ArgumentNullException(nameof(source));

if (source is ICollection<T> collection)
return collection;

return enumerable.ToList();
return source.ToArray();
}

/// <summary>
/// Casts a sequence to a <see cref="IReadOnlyList{T}"/>, otherwise enumerates the sequence.
/// </summary>
/// <param name="enumerable"></param>
/// <param name="source"></param>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static IReadOnlyList<T> AsReadOnlyList<T>(this IEnumerable<T> enumerable)
public static IReadOnlyList<T> AsReadOnlyList<T>(this IEnumerable<T> source)
{
if (enumerable is IReadOnlyList<T> collection)
if (source is null)
throw new ArgumentNullException(nameof(source));

if (source is IReadOnlyList<T> collection)
return collection;

return new ReadOnlyCollection<T>(enumerable.ToList());
return source.ToArray();
}

/// <summary>
/// Casts a sequence to a <see cref="IReadOnlyCollection{T}" />, otherwise enumerates the sequence.
/// </summary>
/// <param name="source"></param>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
public static IReadOnlyCollection<T> AsReadOnlyCollection<T>(this IEnumerable<T> source)
{
if (source is null)
throw new ArgumentNullException(nameof(source));

if (source is IReadOnlyCollection<T> collection)
return collection;

return source.ToArray();
}

/// <summary>
/// Enumerates a sequence and returns only non null values
/// </summary>
/// <param name="enumerable"></param>
/// <param name="source"></param>
/// <typeparam name="T"></typeparam>
/// <returns></returns>
/// <exception cref="ArgumentNullException"></exception>
public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> enumerable) where T : class
public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> source)
{
if (enumerable is null)
throw new ArgumentNullException(nameof(enumerable));
if (source is null)
throw new ArgumentNullException(nameof(source));

foreach (var t in enumerable)
foreach (var t in source)
{
if (t is not null)
yield return t;
Expand All @@ -106,27 +128,26 @@ public static IEnumerable<T> WhereNotNull<T>(this IEnumerable<T?> enumerable) wh
/// <summary>
/// Enumerates a sequence and returns only non null values
/// </summary>
/// <param name="enumerable"></param>
/// <param name="source"></param>
/// <param name="selector"></param>
/// <typeparam name="T"></typeparam>
/// <typeparam name="TResult"></typeparam>
/// <returns></returns>
/// <exception cref="ArgumentNullException"></exception>
public static IEnumerable<TResult> WhereNotNull<T, TResult>(
this IEnumerable<T> enumerable,
this IEnumerable<T> source,
Func<T, TResult?> selector)
where TResult : class
{
if (enumerable is null)
throw new ArgumentNullException(nameof(enumerable));
if (source is null)
throw new ArgumentNullException(nameof(source));

if (selector is null)
throw new ArgumentNullException(nameof(selector));

foreach (var t in enumerable.Select(selector))
foreach (var t in source.Select(selector))
{
if (t is not null)
yield return t;
}
}
}
}
29 changes: 27 additions & 2 deletions src/Primitives/Primitives/test/Extensions/EnumerableExtensionTests.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -18,7 +18,7 @@ public void TryGetFirstValue_Array()
public void TryGetFirstValue_Enumerable()
{
// Where() to force an Enumerable
IEnumerable<int> list = Enumerable.Range(1, 100).Where(x => true);
var list = Enumerable.Range(1, 100).Where(x => true);

Assert.True(list.TryGetFirstValue(out var value));
Assert.Equal(1, value);
Expand All @@ -36,8 +36,33 @@ public void TryGetFirstValue_Empty()
public void TryGetFirstValue_EmptyEnumerable()
{
// Where() to force an Enumerable
IEnumerable<int> list = Enumerable.Range(1, 100).Where(x => false);
var list = Enumerable.Range(1, 100).Where(x => false);

Assert.False(list.TryGetFirstValue(out _));
}

[Fact]
public void WhereNotNull_ValueTypeListContainsNull_ReturnsNoNullValues()
{
int?[] list = [1, null, 2, null, 3];

var result = list.WhereNotNull();

Assert.Equal(result, [1, 2, 3]);
}

[Fact]
public void WhereNotNull_SelectorClassTypeListContainsNull_ReturnsNoNullValues()
{
Test[] list = [new("1"), new(null), new("2"), new(null)];

var result = list.WhereNotNull(x => x.Value);

Assert.Equal(result, ["1", "2"]);
}

private class Test(string? value)
{
public string? Value { get; } = value;
}
}
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