If your .NET application is doing anything useful, it’s working with collections—and if you’re not paying attention, that’s exactly where your performance starts to fall apart.

Collections are everywhere: lists, arrays, dictionaries, spans—you name it. And every decision you make—how you loop, how you sort, how you search, even what type you choose—has a direct impact on performance. Get it right, and your code flies. Get it wrong, and you’re dragging unnecessary overhead through every execution path.

This page is packed with benchmark-driven, real-world insights into how collections actually behave under the hood. You’ll see the performance differences between reference types, value types, and records, along with the fastest ways to iterate, compare, and manipulate your data.

No fluff. No “it depends” hand-waving. Just hard data and practical guidance you can apply immediately to write faster, tighter, more efficient code.

Bottom line: collections aren’t just a convenience—they’re a performance battlefield. Master them, and your code will scream. Ignore them, and your app will feel like it’s stuck in the opening act.

Collection Performance: The Fastest Way To Iterate Over a Collection in .NET!

Collection Performance: Adding Items to a Collection

Collection Performance: Efficiently Checking for Items in a Collection

Collection Performance: Creating a List<> Using The Task.Parallel Library

Collection Performance: Creating New Collection From A Collection Using for() & foreach()

Unlocking Hidden Performance in Microsoft .NET: Iterating Over IEnumerable with the Enumerator

Collection Performance: Iterating Through Reference Value, and Record Types

Collection Performance: Looping Over a Collection

Collection Performance: Looping Over Reference Type vs. Value Type

Collection Performance: Optimizing Sequence Comparison

Collection Performance: Exercise Caution When Using Take() with a Basic Count

Optimizing Collection Examination: A Comparative Analysis of Predicate Methods in C#

Evaluating the Parallel Processing of Collections in Microsoft .NET

Unlock Performance Gains in .NET: The Power of Custom Comparers

Array Types

Boost Your .NET Projects: Efficient Byte Array Conversions

Microsoft .NET Code Analysis: Creating Empty Arrays

Boost Your .NET Projects: Find the Fastest Way to Get an Item’s Index in Arrays

Collection Performance: Looping Over Collection – Array vs. List

Collection Performance: Exploring the Performance Impacts of Array Properties

Collection Performance: Converting Byte Array to Memory<> and ReadOnlyMemory<>

Microsoft .NET Code Analysis: Improve .NET Performance by Reusing Constant Arrays

Boosting Loop Performance in .NET: The Simple Trick of Caching Array Length

Collection Performance: High-Performance Collection Randomization in .NET

Dictionary Types

Microsoft .NET Code Analysis: Eliminating Dictionary Double Lookups

Collection Performance: Enhancing Dictionary Performance with FrozenDictionary

Collection Performance: SortedDictionary vs Dictionary

Collection Performance: Adding Items To a Dictionary

Collection Performance: Comparing Key Search Methods in Dictionaries

256 Seconds with dotNetDave: Be careful using ContainsKey() with Dictionary Types

Optimizing Dictionary Performance in .NET: SortedDictionary vs. Dictionary

Immutable Collection Types

Collection Performance: Creating New Immutable Collection From a Collection

Collection Performance: Creating Immutable Sorted Collections

Other Collection Types

Collection Performance: A Comprehensive Benchmark Analysis of Collection Types in .NET Beyond Arrays and Lists

Collection Performance: Creating A New List Or Linkedlist While Adding Items Using The Constructor

Collection Performance: Introducing FrozenSet in .NET 8: Benefits and Benchmark PerformanceCollection Performance

Collection Performance: Introducing FrozenSet in .NET 8: Benefits and Benchmark PerformanceCollection Performance

Sorting and Sorted Collection Types

Collection Performance: Sorting Collections

Collection Performance: Sorting the Record Type

Collection Performance: Creating New Sorted Collection From a Collection

Collection Performance: Sort() with CompareTo()

Spans

Collection Performance: Looping Over a Collection Using Span and ReadOnlySpan

Collection Performance: Harnessing AsSpan() for Byte Array Conversion

Supercharging .NET Collections with Span and MemoryExtensions

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