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C# .NET 8 Frozen Collections: An Introduction to Super Fast Data Access

C# .NET 8 Frozen Collections: An Introduction to Super Fast Data Access

Introduction to Frozen Collections: Super-fast data access with C# and .NET Core!

Hello! I'm John, a veteran blog writer. When you hear about AI technology, you might think it sounds difficult. But don't worry! In this blog, I'll explain the latest technology in an easy-to-understand way for everyone. This time, I'll talk about "Frozen CollectionsLet's take a look at this technology together, especially for those of you who are just starting to use C# and .NET Core!


Eye-catching visual of frozen collections, C#, .NET Core and AI technology vibes

What is the Frozen Collection? Basic information you should know

First, let me explain the word "collection". In programming, we use a container called a "collection" to handle a lot of data (for example, a list of users or product information) together. There are various types of collections, such as lists, dictionaries, and sets.

Now, to the main topic:Frozen Collection".this is,.NET 8 This is a special collection introduced in the relatively new version of .NET. As the name "Frozen" suggests, it is "frozen" in other words.Once created, the contents cannot be changedThis is a major feature. And thanks to this property of being "unchangeable",Reading data (especially searching) becomes much fasterIt is optimized like this.

To put it in perspective, it's like a "perfect reference book" that once completed, no one can tamper with it. You can't add pages or rewrite the contents, but on the flip side, it's very quick to search for specific information from the index.

This frozen collection solves the problem that programmers want: "Create the data just once, and then just read it. And read it as quickly as possible!" This is especially important for web services that are accessed by many people at the same time, where the speed of reading is directly linked to the comfort of the service, making this a very important technology.

To summarise its unique features:

  • Immutability: Cannot be changed after creation.
  • Fast read speed: Data search and reference is extremely fast.
  • Thread safetySafe for simultaneous access by multiple program processes (more on this later).

Why do we need a frozen collection? How is it different from a traditional collection?

You may be wondering, "Why do we need something new when we already have so many collections?" That's a great question! Each of the previous collections had their strengths and weaknesses.

Challenges with traditional collections

  • List<T> (list):

    This is one of the most common collections, and stores data in an ordered order. It is easy to add or remove elements, but searching for a specific item among a lot of data tends to take longer as the amount of data increases (because it is searched in order from the beginning).

  • Dictionary<TKey, TValue> (dictionary) / HashSet<T> (Hashset):

    These are collections that make it very fast to find specific data.Dictionary manages data in "key" and "value" pairs,HashSet efficiently manages non-overlapping elements. However, because they can be freely changed even after creation (mutable), unexpected problems (such as data inconsistency) can occur when multiple processes try to rewrite data at the same time. To avoid this, a somewhat complicated mechanism called "locking" may be required.

  • ImmutableList<T> (Immutable List) / ImmutableHashSet<T> (Immutable hash sets) etc.:

    "Immutable" means "unchangeable." These collections also cannot be modified once they are created. If you try to modify them, a "new" collection is created to reflect the changes, leaving the original collection alone. This makes your data more secure, but it is not as heavily optimized for read speed as frozen collections.

What the Frozen Collection solves

The Frozen Collection addresses these challenges, especiallyRead performance"When"Thread safety for simultaneous access from multiple processes" was developed with a focus on

By working on the premise that data is "created once and never changed," the internal structure can be optimized for reads, allowing for much faster searches than traditional immutable collections.

In addition, because the data never changes, even if multiple processes (called threads) refer to the same frozen collection at the same time, there is no need to worry about the data being corrupted or becoming strange values. This makes it unnecessary to write complex synchronization processes (such as locks), making programs simpler and safer.

Digging deeper into the key features of the Frozen collection!

Let's take a closer look at what makes the Frozen collection so appealing.

  • Immutability

    This is the core feature of frozen collections: you cannot add, remove, or change any elements in a collection once it has been created. This guarantees data consistency. You don't need to worry about the values ​​you set changing over time.

  • Performance Optimization

    Frozen collections are designed to be extremely fast, especially for read operations such as searching and referencing data. They are designed with ingenuity at the data structure and algorithm level, allowing you to quickly find what you are looking for among a large amount of data. Although there may be some cost at the time of initialization (when creating a collection), the subsequent improvement in read speed more than makes up for it.

  • Thread Safety

    A "thread" is a sequence of operations within a program. Modern applications use multiple threads running simultaneously to increase efficiency (for example, a web server processes many user requests at the same time). Frozen collections are immutable, so even if multiple threads access the same collection at the same time, there are no race conditions or synchronization issues. This makes otherwise complex concurrent programming much easier and safer.

  • Simplicity

    Usage is very simple: select an existing collection (e.g.List , Dictionary) allows you to create frozen collections with a single simple method call. The API (Application Programming Interface: a window for calling program functions) is also similar in many ways to conventional collections, making it attractive for its low learning cost.


frozen collections, C#, .NET Core AI technology illustration

Frozen Collection Types: FrozenDictionary and FrozenSet

.NET 8 System.Collections.Frozen The namespace provides two main frozen collections:

  • FrozenDictionary<TKey, TValue> (Frozen Dictionary)

    This is a frozen version of a "dictionary" that stores key-value pairs. Dictionary<TKey, TValue> As with the above, you can quickly retrieve values ​​using keys, but once created, you cannot add, change, or delete keys or values. For example, it is ideal for cases where the product master data does not change after initialization, such as retrieving the "product name" using the "product ID" as a key.

  • FrozenSet<T> (Frozen set)

    This is a frozen version of a "set" that stores a collection of distinct elements. HashSet<T> You can quickly determine whether a particular element exists in a set. This also cannot be changed after creation. For example, it is suitable for handling a set of unique values ​​that do not change once defined, such as a "list of allowed user names."

What both collections have in common isIt is read-only and cannot be modified after creation." This constraint is what produces the amazing read performance.

Let's try using Frozen Collections in C#! Practical code example

Let's take a look at how frozen collections are actually used in C# code, assuming a simple console application.

Preparation: .NET environment

The Frozen Collection .NET 8 and laterAvailable in Visual Studio 2022 and Visual Studio Code. Create a project targeting .NET 8 (or later) in a development environment such as Visual Studio XNUMX or Visual Studio Code. A console application is recommended.

FrozenDictionary Creating and Using

First, the usual Dictionary Prepare and then FrozenDictionary Let's create it.


using System.Collections.Frozen; // これが必要！

// 1. まずは通常のDictionaryを用意
var regularDictionary = new Dictionary<int, string>
{
    { 1, "リンゴ" },
    { 2, "バナナ" },
    { 3, "ミカン" }
};

// 2. ToFrozenDictionary() メソッドでフローズン化！
var frozenDictionary = regularDictionary.ToFrozenDictionary();

// 3. データの読み取り (高速！)
if (frozenDictionary.TryGetValue(2, out string? fruitName))
{
    Console.WriteLine($"キー2の果物: {fruitName}"); // 出力: キー2の果物: バナナ
}

if (frozenDictionary.ContainsKey(3))
{
    Console.WriteLine($"キー3は存在します。値は {frozenDictionary[3]} です。"); // 出力: キー3は存在します。値は ミカン です。
}

// 4. 変更しようとすると…？
// frozenDictionary.Add(4, "ブドウ"); // これはコンパイルエラー！変更できません。
// frozenDictionary[1] = "赤いリンゴ"; // これもコンパイルエラー！

ToFrozenDictionary() By simply calling this extension method, you can quickly create a frozen dictionary.TryGetValue , ContainsKey, Indexer (frozenDictionary[key]) to read the data. Easy as that!

FrozenSet Creating and Using

next,FrozenSet Let's take a look at an example of building from a list.


using System.Collections.Frozen; // これも必要！

// 1. まずは通常のListを用意 (HashSetからでもOK)
var regularList = new List<string> { "犬", "猫", "鳥", "犬" }; // "犬"が重複

// 2. ToFrozenSet() メソッドでフローズン化！
// 重複は自動的に除去されます (セットの性質)
var frozenSet = regularList.ToFrozenSet();

// 3. 要素の存在確認 (高速！)
if (frozenSet.Contains("猫"))
{
    Console.WriteLine("猫はセットに含まれています。"); // 出力: 猫はセットに含まれています。
}

if (!frozenSet.Contains("魚"))
{
    Console.WriteLine("魚はセットに含まれていません。"); // 出力: 魚はセットに含まれていません。
}

Console.WriteLine($"セットの要素数: {frozenSet.Count}"); // 出力: セットの要素数: 3 (重複が除去されたため)

// 4. 変更しようとすると…？
// frozenSet.Add("ハムスター"); // これもコンパイルエラー！変更できません。

ToFrozenSet() The method makes it easy to extract values ​​from various collections, such as lists and hash sets. FrozenSet You can make.Contains Methods allow you to quickly check whether a particular element is included.

Performance Comparison: Are Frozen Collections Really Faster?

You may be wondering, "Is it really that fast?" In fact, there are benchmark (performance measurement) results that compare various types of collections and read speeds.

For example, according to an Infoworld article (one of the sources for this article):FrozenSet are the same immutable collections. ImmutableHashSet Faster search than, and potentially mutable HashSet It is said that it can sometimes show faster lookup performance thanList When compared to the above, the difference is clear.FrozenSet is overwhelmingly faster.

Specifically, the following trends are observed (although they may vary slightly depending on the number of elements and the content of the data):

  • Search speed (image from fastest to slowest):
    1. FrozenSet / FrozenDictionary (Very fast)
    2. HashSet / Dictionary (fast)
    3. ImmutableHashSet / ImmutableDictionary (Fairly fast)
    4. List (The more elements there are, the slower it gets.)

However, there is one thing to note. Frozen collections optimize their internal structure when they are created in order to maximize read performance.The cost (time and CPU load) of creating a collection is:HashSet It's a bit more expensive than a mutable collection likeYou may.

Therefore, it is not suitable for data that is "frequently created and destroyed."The Frozen Collection really shines in a scenario where you create it once and then just keep reading it.

How to use the Frozen Collection: In what situations is it useful?

Frozen collections are especially useful in the following cases:

  • Application configuration data:

    It's perfect for storing configuration values ​​that are loaded from a file or database at program startup and don't change afterwards (e.g. API endpoint URLs, timeouts, enabled feature flags, etc.).

  • Master Data and Static Lookup Tables:

    These are data sets that are frequently referenced but have fixed content, such as a table showing the correspondence between country codes and country names, a table showing the correspondence between postal codes and addresses, and a table showing the correspondence between category IDs and category names.

  • Frequently accessed read-only cache:

    It can be used when you want to cache data that does not change for a certain period of time once it has been obtained, such as calculation results or results obtained from an external API, and access it quickly.

  • Allowed and banned lists:

    This is data that requires fast existence verification for security-related checks, such as lists of allowed IP addresses, lists of banned words, etc.

  • Defining state machines and command patterns:

    They are also useful for storing static information that forms the basis of a program's operational logic, such as transition rules from one state to the next, or mappings of processing commands to specific inputs.

  • Immutable data in a singleton service in an ASP.NET Core application:

    If a service that is registered as a singleton in the Dependency Injection (DI) container contains an immutable collection of data, frozen collections provide fast access to that data.

When should you use it? How to use it wisely with other collections

The Frozen Collection is not an all-purpose product. It is important to understand its characteristics and use it appropriately in combination with other collections.

List<T> When to use:
The order of elements is important and you want to allow duplicates. Data is added and removed frequently and search speed is not a major concern.
Dictionary<TKey, TValue> , HashSet<T> When to use:
When fast access by key or fast existence checking for unique elements is required, and the data may change frequently. Thread safety is an additional consideration.
ImmutableList<T>, ImmutableDictionary<TKey, TValue>, ImmutableHashSet<T> When to use:
You want data immutability but don't need the extreme read performance optimizations of frozen collections, or you're okay with creating a new instance every time you make a change.
FrozenDictionary<TKey, TValue>, FrozenSet<T> When to use:
This is the most important point!

  • DataOnce created, it never changesこと.
  • For that dataRead access (especially searches) is very frequentこと.
  • The cost of production is acceptable, butI want to maximize read performance.こと.
  • I want thread safety to be guaranteed naturallyこと.

When these conditions are met, the Frozen Collection performs at its best.

When in doubt, ask yourself, "Is there a chance that this data could have changed even once since I created it?" and "How often will I find myself looking for something in this data?"

Cautions and considerations: Things you should know before using

Frozen collections are powerful, but there are some things to keep in mind:

  • Creation cost:

    As mentioned above, to optimize read performance, creation may take longer than normal collections, so it is best to create them at a time when you have plenty of time, such as when your application starts up.

  • Complete immutability:

    You really can't change anything - if you need to update the contents of the data, you have to destroy the original frozen collection and "recreate" it with the new data.

  • Memory usage:

    Depending on how you optimize, there is a chance that memory usage may increase slightly, but in most cases the benefits of improved read performance will outweigh this. The best way to get specific numbers is to test it out for yourself in your application.

  • .NET 8 or later required:

    This feature was introduced in .NET 8. It is not available in older versions of .NET Framework or .NET Core, so please check your project's target framework.


Future potential of frozen collections, C#, .NET Core represented visually

A little bit of what experts have to say and the future of the Frozen Collection

Many .NET developers and experts have welcomed the arrival of frozen collections. They often say, "It will greatly contribute to improving the performance of read-heavy applications!" Their effectiveness has been introduced in the Microsoft .NET team blog and in commentary articles by well-known technology evangelists.

Frozen collections is a relatively new feature that was introduced in .NET 8, but the .NET platform is constantly evolving. We can expect further performance improvements and more useful features to be added to the entire collection library in the future!

Frequently Asked Questions (FAQ) – Solving beginners’ questions!

Q1: What type of data is frozen collections best used for?
A1: It is best suited for data that does not change from when the application is launched until it is closed. For example, so-called "master data" or "setting data" such as setting values ​​that are not changed once loaded, country lists, product category lists, etc. It is effective when such data is frequently searched.
Q2: ImmutableList , ImmutableHashSet When,FrozenSet What is the biggest difference?
A2: Both are the same in that they are "immutable (the contents do not change)". The main difference is,FrozenSet (or FrozenDictionary) has been optimized to maximize read performance (search speed, etc.)It is a point.ImmutableCollections of this type are also immutable and safe,FrozenIt is good to remember that the system is further specialized for reading.
Q3: What if I create a frozen collection and then decide I want to add just one more piece of data?
A3: Unfortunately, you cannot add data to a frozen collection later. If you need to make changes,"Recreate" the Frozen Collection itself by adding new elements to the original dataIt is necessary to take this "cost of recreating" into consideration and use it for data that will not change.
Q4: Which versions of .NET can use frozen collections?
A4: .NET 8 and laterIn your project settings, make sure your target framework is set to .NET 8 or higher.
Q5: FrozenDictionary と FrozenSet Do you have any other Frozen collections?
A5: As of .NET 2024 in early 8,System.Collections.Frozen The main namespace provided is this FrozenDictionary<TKey, TValue> と FrozenSet<T> There are two types of frozen collections. It is possible that new types of frozen collections will appear in future .NET updates.

Summary: The Frozen Collection makes app development easier!

This time, I will explain the new feature of .NET 8, "Frozen Collections," in an easy-to-understand way even for beginners. Let's review the main points again.

  • The Frozen Collection isOnce created, it cannot be changed (immutable)collection.
  • Instead,Data reading (especially searching) is extremely fast!
  • FrozenDictionary と FrozenSet There are two main types:
  • It is extremely useful in scenarios where data is fixed and read very frequently.
  • It is thread-safe, so you can safely access it from multiple processes simultaneously.

Frozen collections are a powerful tool that can greatly improve the performance of your applications if used properly. Try to find ways to use them in your C#/.NET Core projects!

I hope this article will help you in your programming studies. Learning new technology is exciting, isn't it? I'll continue to strive to provide easy-to-understand explanations, so please look forward to it!

note: This article is for informational purposes only, and is not an absolute recommendation for any particular technology choice. Please select the most appropriate technology after thorough testing and validation based on the requirements and characteristics of your project.

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Frozen Collections, C#, .NET Core, Performance Optimization, Immutable Collections

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