sealed keyword means that the class cannot be inherited. Declaring the constructor as private means that no instance of the class can be created.
You can have a base class with a private constructor but still inherit from that base class, define some public constructors, and effectively instantiate the base class.
Constructors is not inherited (so the derived class won't just because the base class has all private constructors), and the derived class always calls the base class constructor first.
Marking a class as sealed prevents someone from working around your carefully constructed singleton class because it prevents someone from inheriting from the class.
Example
static class Program { static void Main(string[] args){ Singleton fromStudent = Singleton.GetInstance; fromStudent.PrintDetails("From Student"); Singleton fromEmployee = Singleton.GetInstance; fromEmployee.PrintDetails("From Employee"); Console.WriteLine("-------------------------------------"); Singleton.DerivedSingleton derivedObj = new Singleton.DerivedSingleton(); derivedObj.PrintDetails("From Derived"); Console.ReadLine(); } } public class Singleton { private static int counter = 0; private static object obj = new object(); private Singleton() { counter++; Console.WriteLine("Counter Value " + counter.ToString()); } private static Singleton instance = null; public static Singleton GetInstance{ get { if (instance == null) instance = new Singleton(); return instance; } } public void PrintDetails(string message){ Console.WriteLine(message); } public class DerivedSingleton : Singleton { } }
The above is the detailed content of Why are singleton classes in C# always sealed?. For more information, please follow other related articles on the PHP Chinese website!

C# and .NET runtime work closely together to empower developers to efficient, powerful and cross-platform development capabilities. 1) C# is a type-safe and object-oriented programming language designed to integrate seamlessly with the .NET framework. 2) The .NET runtime manages the execution of C# code, provides garbage collection, type safety and other services, and ensures efficient and cross-platform operation.

To start C#.NET development, you need to: 1. Understand the basic knowledge of C# and the core concepts of the .NET framework; 2. Master the basic concepts of variables, data types, control structures, functions and classes; 3. Learn advanced features of C#, such as LINQ and asynchronous programming; 4. Be familiar with debugging techniques and performance optimization methods for common errors. With these steps, you can gradually penetrate the world of C#.NET and write efficient applications.

The relationship between C# and .NET is inseparable, but they are not the same thing. C# is a programming language, while .NET is a development platform. C# is used to write code, compile into .NET's intermediate language (IL), and executed by the .NET runtime (CLR).

C#.NET is still important because it provides powerful tools and libraries that support multiple application development. 1) C# combines .NET framework to make development efficient and convenient. 2) C#'s type safety and garbage collection mechanism enhance its advantages. 3) .NET provides a cross-platform running environment and rich APIs, improving development flexibility.

C#.NETisversatileforbothwebanddesktopdevelopment.1)Forweb,useASP.NETfordynamicapplications.2)Fordesktop,employWindowsFormsorWPFforrichinterfaces.3)UseXamarinforcross-platformdevelopment,enablingcodesharingacrossWindows,macOS,Linux,andmobiledevices.

C# and .NET adapt to the needs of emerging technologies through continuous updates and optimizations. 1) C# 9.0 and .NET5 introduce record type and performance optimization. 2) .NETCore enhances cloud native and containerized support. 3) ASP.NETCore integrates with modern web technologies. 4) ML.NET supports machine learning and artificial intelligence. 5) Asynchronous programming and best practices improve performance.

C#.NETissuitableforenterprise-levelapplicationswithintheMicrosoftecosystemduetoitsstrongtyping,richlibraries,androbustperformance.However,itmaynotbeidealforcross-platformdevelopmentorwhenrawspeediscritical,wherelanguageslikeRustorGomightbepreferable.

The programming process of C# in .NET includes the following steps: 1) writing C# code, 2) compiling into an intermediate language (IL), and 3) executing by the .NET runtime (CLR). The advantages of C# in .NET are its modern syntax, powerful type system and tight integration with the .NET framework, suitable for various development scenarios from desktop applications to web services.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

Dreamweaver Mac version
Visual web development tools

mPDF
mPDF is a PHP library that can generate PDF files from UTF-8 encoded HTML. The original author, Ian Back, wrote mPDF to output PDF files "on the fly" from his website and handle different languages. It is slower than original scripts like HTML2FPDF and produces larger files when using Unicode fonts, but supports CSS styles etc. and has a lot of enhancements. Supports almost all languages, including RTL (Arabic and Hebrew) and CJK (Chinese, Japanese and Korean). Supports nested block-level elements (such as P, DIV),

SublimeText3 Chinese version
Chinese version, very easy to use

WebStorm Mac version
Useful JavaScript development tools

MinGW - Minimalist GNU for Windows
This project is in the process of being migrated to osdn.net/projects/mingw, you can continue to follow us there. MinGW: A native Windows port of the GNU Compiler Collection (GCC), freely distributable import libraries and header files for building native Windows applications; includes extensions to the MSVC runtime to support C99 functionality. All MinGW software can run on 64-bit Windows platforms.