Typecasting in C#

Question

What is type casting, what\'s the use of it? How does it work?

Answer 1

Casting means creating a reference to an object that is of a different type to the reference you're currently holding. You can do upcasting or downcasting and each has different benefits.

Upcasting:

string greeting = "Hi Bob";
object o = greeting;

This creates a more general reference (object) from the more specific reference (string). Maybe you've written code that can handle any object, like this:

Console.WriteLine("Type of o is " + o.GetType());

That code doesn't need to be changed no matter what objects you set o to.

Downcasting:

object o = "Hi Bob";
string greeting = (string)o;

Here you want a more specific reference. You might know that the object is a string (you can test this e.g.:

if (o is string)
{ do something }

Now you can treat the reference as a string instead of an object. E.g. a string has a length (but an object doesn't), so you can say:

Console.WriteLine("Length of string is " + greeting.length);

Which you can't do with an object.