C# & VB.NET Conversion Pocket Reference

Object-Oriented Features

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End Sub

End Class

In this case, the code in the constructor for Account calls the

Account version of MakeDeposit. Note that

MyClass is not

the same as

Me in VB. Using Me would still call the derived

version instead of the original version.

Requiring/Preventing Inheritance

In C# you can mark a class as sealed. A sealed class is a class

that cannot be used as a base class for another class—in

other words, you cannot inherit from it. Here is an example

of adding the word “sealed” to the class definition:

class Account

{

}

sealed class Checking : Account

{

}

//***this is illegal***

class SuperChecking : Checking

{

}

In this code example, Account is not sealed, so Checking can

inherit from it; however, Checking is a sealed class, so it is

illegal for SuperChecking to inherit from it. This is not the

place to have a full discussion of why you would seal, but

normally you would seal a class to prevent someone from

writing a subclass that overrides how you implemented an

interface. Take for example the System.String class that

Microsoft provides. It implements a series of critical inter-

faces: ICloneable, IComparable, etc. The runtime expects

these interfaces to be implemented in a particular way. It

would cause problems if you were to write your own string

class and override the way those interfaces are implemented,

and then pass instances of your string class to functions in

the runtime