C# Classes

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Permalink Reply by peter fotiadis on October 29, 2015 at 2:18am

Er... hmm ...I would strongly suggest some proper reading (forget Internet: you can't learn programming that way):

The bible PlanA: C# In depth (Jon Skeet).
The bible PlanB: C# Step by step (John Sharp).
The bible PlanC: C# 5.0/6.0 (J/B Albahari) > my favorite

The reference: C# Language specs  ECMA-334

The candidates:
C# Fundamentals (Nakov/Kolev & Co)
C# Head First (Stellman/Greene)
C# Language (Jones)

Permalink Reply by David Rutten on October 29, 2015 at 4:45am

You can define a new class using the class keyword:

[private/protected/internal/public] [static/abstract/sealed] class MyClassName

{

  // Class fields, constructors, properties and methods go here.

}

If you do not pick a scope specifier, then you'll get the default but I can never remember what the default is so I always specify a scope.

• private means only the code inside the same scope can 'see' your class. In fact with classes this only makes sense if you define a class inside another class, so you probably never use private for classes.
• protected means only code inside the same scope or an inherited scope can see your class. Again, protected is rare for classes.
• internal means only code in the same assembly can see the class. This is quite common, it means you do not want anyone else to use that class.
• public means everyone can see the class.

When a class is marked static, it may only contain static methods and fields. This means nobody ever constructs your class, all the functionality is available all the time via the class name, rather than via a class instance. Most classes are not static. A famous example of a class which is static is System.Math.

When a class is marked abstract, it means you cannot create instances of that class. Instead, the only way to use that class is to make another class which derives from the abstract class. I didn't include notation for class inheritance or interface implementations, you can read up on that online.

When a class is marked sealed, it means nobody can inherit from it. It's the proverbial end of the line.

Most often, what works well is simply:

public class MyClassName

{

 // class content here...

}