Upcasting and Downcasting

Upcasting: Creating a base (Parent) class reference from a subclass (Child) reference. Upcasting is performed explicitly (No need of casting)

Downcasting: Creating a subclass (Child) class reference from a base (Parent) class reference

Is and As Keyword

The “Is” keyword is used to check if an object is of a particular type
The “As” keyword is used to convert from one type to another in a safe way without raising any Exception. If casting is not possible it will return null

Up-casting and Down-casting in C# Inheritance - Interview Sansar

using System;
 
namespace UpcastingDowncasting
{
		public class Text : Shape
		{
			public int FontSize { get; set; }
			public string FontText { get; set; }
		}
 
		public class Shape
		{
			public int Width { get; set; }
			public int Height { get; set; }
			public int X { get; set; }
			public int Y { get; set; }
 
			public void Draw()
			{
				Console.WriteLine("Draw from the Shape Class");
			}
		}
 
		class Program
		{
			static void Main(string[] args)
			{
				// Upcasting
				Text text = new Text();
				Shape shape = text;
 
				text.Width = 200;
				shape.Width = 100;
				Console.WriteLine(shape.Width);
 
				// Downcasting
				Shape shape1 = new Text();
				Text text1 = (Text)shape1;
				Console.WriteLine(text1.FontSize);
 
				// Check type of variable
				if (text1 is Text)
					Console.WriteLine("Object Type : Text");
 
				// Try to Cast
				Text text2 = shape1 as Text;
				if (text2 != null)
					Console.WriteLine("Conversion Successful");
			}
		}
}

Note

When we perform upcasting and/ or downcasting both references are still pointing to the same object just the view of the object changes