Derived types must be completely substitutable for their base types.Definition:We should be able to treat a child class as though it were the parent class. Essentially this means that all derived classes should retain the functionality of their parent class and cannot replace any functionality the parent provides.Before Liskov Substitutionpublic ... Read More

The sealed keyword means that the class cannot be inherited from. Declaring constructors private means that instances of the class cannot 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 that base class.Constructors are ... Read More

To get the files, C# provides a method Directory.GetFilesDirectory.GetFiles returns the names of all the files (including their paths) that match the specified search pattern, and optionally searches subdirectories.In the below example * is matches Zero or more characters in that position.SearchOption TopDirectoryOnly. Searches only the top directoriesSearchOption AllDirectories .Searches ... Read More

We should use an IDisposable design pattern (or Dispose Pattern) when we need to dispose of unmanaged objects.For implementing the IDisposable design pattern, the class which deals with unmanaged objects directly or indirectly should implement the IDisposable interface.And implement the method Dispose declared inside of the IDisposable interface. We do ... Read More

The null object pattern helps us to write a clean code avoiding null checks where ever possible. Using the null object pattern, the callers do not have to care whether they have a null object or a real object. It is not possible to implement null object pattern in every ... Read More

These are used to import namespaces (or create aliases for namespaces or types).These go at the top of the file, before any declarations.using System; using System.IO; using WinForms = global::System.Windows.Forms; using WinButton = WinForms::Button;The using statement ensures that Dispose() is called even if an exception occurs when you are creating ... Read More

To get the directories C# provides a method Directory.GetDirectoriesDirectory.GetDirectories returns the names of the subdirectories (including their paths) that match the specified search pattern in the specified directory, and optionally searches subdirectories.To get the files, C# provides a method Directory.GetFilesDirectory.GetFiles returns the names of all the files (including their paths) ... Read More

In synchronous C# code, the exceptions are propagated up the call stack until they reach an appropriate catch block that can handle the exception. However, exception handling in asynchronous methods is not as straightforward.An asynchronous method in C# can have three types of return value: void, Task, and Task. When ... Read More

To get the directories C# provides a method Directory.GetDirectories. The Directory.GetDirectories method returns the names of the subdirectories (including their paths) that match the specified search pattern in the specified directory, and optionally searches subdirectories.In the below example * is matches Zero or more characters in that position. SearchOption TopDirectoryOnly ... Read More

IEnumerable is an interface defining a single method GetEnumerator() that returns an IEnumerator interface. It is the base interface for all non-generic collections that can be enumerated.This works for read-only access to a collection that implements that IEnumerable can be used with a foreach statement.List class represents the list of ... Read More