What is the use of static class in C# and .NET with examples?

In C# and .NET, a static class is a class that cannot be instantiated, and all its members (fields, properties, methods, etc.) must be static. This means that you can't create an instance of a static class, and you access its members using the class itself rather than an instance of the class. Static classes are often used to group related functionality together and provide a convenient way to organize code.Here are some common use cases for static classes in C# and .NET:1. **Utility Classes:** Static classes are commonly used to create utility classes that contain methods for common tasks, calculations, or operations. For example: ```csharp public static class MathUtilities { public static double Square(double number) { return number * number; } public static int Add(int a, int b) { return a + b; } } ``` Usage: ```csharp double squaredValue = MathUtilities.Square(5); int sum = MathUtilities.Add(3, 7); ```2. **Helper Classes:** Static classes can be used to create helper classes that provide shared functionality across an application. For instance: ```csharp public static class FileHelper { public static string ReadFile(string filePath) { // Code to read and return content from a file } public static void WriteFile(string filePath, string content) { // Code to write content to a file } } ``` Usage: ```csharp string fileContent = FileHelper.ReadFile("example.txt"); FileHelper.WriteFile("output.txt", "Hello, world!"); ```3. **Constants and Configuration:** You can use static classes to store constant values or configuration settings that are shared across the application: ```csharp public static class AppConfig { public const string ConnectionString = "your_connection_string_here"; public const int MaxRetryAttempts = 3; } ``` Usage: ```csharp string connectionString = AppConfig.ConnectionString; int maxRetries = AppConfig.MaxRetryAttempts; ```Remember that static classes cannot be instantiated, so they don't have constructors, and you can't create instances of them using the `new` keyword. They are typically used when you have functionality that does not depend on maintaining state across multiple instances. read less