The CollectionExtensions class in the DotNetTips.Spargine.Extensions project was created to eliminate that friction. It provides a focused set of high-performance, defensive, and developer-friendly extension methods that enhance ICollection<T> without changing how you think about collections. These extensions reduce boilerplate code, enforce safer usage patterns, and unlock modern .NET performance features such as spans and frozen collections—all while remaining easy to adopt in existing projects. This article documents the available methods in CollectionExtensions and explains how they can simplify your code while improving correctness and runtime efficiency

Methods

Here is a list of the current methods available in the CollectionExtensions class:

• AddIf(T item, bool condition)
  Adds an item to the ICollection if a specified condition is met. It validates that both the collection and the item to be added are not null.
• AddIfNotExists(T item, IEqualityComparer<T>? comparer = null)
  Adds the specified item to the collection if it does not already exist.
• AddRange(IEnumerable<T> items, bool ensureUnique)
  Adds multiple items to the ICollection. It validates that both the collection and the items are not null. The ensureUnique parameter ensures that the items added are unique.
• AsReadOnlySpan()
  Converts a collection to a ReadOnlySpan, which may improve performance.
• AsSpan()
  Converts the collection to a Span, which may improve performance.
• ToFrozenSet()
  Converts a collection to a FrozenSet, which may improve performance.
• Upsert<T, TKey>(item)
  Upserts (updates or inserts) the specified item into the collection.

Summary

The CollectionExtensions class is designed to make everyday collection operations safer, cleaner, and faster. By eliminating repetitive patterns, enforcing defensive checks, and embracing modern .NET performance features, these extensions help you write code that is easier to maintain and more efficient at runtime.

If your applications rely heavily on collections—and most do—these enhancements can deliver immediate gains in code quality, reliability, and performance with minimal effort.

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